A game which takes place in or refers to another video game, but isn't really a sequel. It can be a simple side story, a Perspective Flip, or a chance to give a popular character background they didn't get in the original game. The major stipulation is it is not usually required to canonically fit into the main game or require having played it to enjoy. Gaiden Games are sometimes titled from the direct translation of the Japanese word gaiden, meaning "another story". Frequently, these games are released on portables or less-powerful systems, but modified appropriately. They are often lower budget and can be seen as cash-ins, but can be interesting if they choose a different viewpoint, poke fun at the original, or are simply more innovative than a large-budget game might be allowed to be. Subtrope of Spin-Off. Sister trope to Pinball Spinoff. Also of note is that having Gaiden in its title doesn't necessarily mean the game pertains to this trope. Even if you exclude Ninja Gaiden, which has a troubled approach with its gaiden status. See the respective entry below.
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- Metal Gear: Ghost Babel and the two Metal Gear Ac!d games are officially recognize as "Gaiden" games in the Metal Gear series (see here), even though they don't really fit in the series' canon in any way.
- Christmas NiGHTS is this for the NiGHTS into Dreams... series. However, it was added onto the Updated Re-release released only in Japan for PS2, and the American digital distribution release.
- Warriors Orochi is a gaiden crossover between Samurai Warriors and Dynasty Warriors.
- The Virtua Fighter series has Virtua Quest (released in Japan as Virtua Fighter: Cyber Generation), a beat-em-up set in the Cyberspace. The original Virtua Fighter roster appears as ghost data that bestow their fighting techniques upon the player.
- The first three Tomb Raider games were eventually re-released as the "Tomb Raider Gold" series, and each game got its own Gaiden Game. TR1 had Unfinished Business, TR2 had Golden Mask and TR3 had Lost Artifact.
- The downloadable game Lara Croft and the Guardian of Light seems to also be this, not taking place in the continuities of the original Core Design series or the Crystal Dynamics-developed games.
- God of War: Chains of Olympus (a prequel to the original game)
- Every Grand Theft Auto game from GTA III to San Andreas was a Gaiden Game; they all took place in the same universe and had some recurring characters, but took place in three different decades (the Stories games took place a few years before Vice City and III) and locations. Other than a few characters who appear in multiple games, the storylines are completely unrelated and don't affect one another. Grand Theft Auto IV totally remakes the universe with a brand new Liberty City, though Vice City and San Andreas are confirmed to exist.
- Mafia II is branded by most as a Spiritual Successor to the the first game, but it's technically a gaiden as it shares the same universe with the original Mafia in a similar fashion with GTA.
- Metal Gear Solid: Portable Ops (taking place between Metal Gear Solid 3: Snake Eater and Metal Gear Solid: Peace Walker) is unique in that while you don't have to play it to understand the story of Metal Gear, it makes it easier to understand the story as the ending reveals how The Patriots where created, and fills in how the Philosophers became the Patriots. They didn't. It also shows us that Sokolov didn't die after all.
- In the The Legend of Zelda series, most major installments involve a new protagonist but there will often be a Gaiden Game to continue that one's story, usually without any appearances by Zelda, Ganon, or the Kingdom Of Hyrule:
- The Legend of Zelda: Link's Awakening involves the Link from The Legend of Zelda: A Link to the Past on waking up on a mysterious Island. Later, a Cap Com / Nintendo colab brought us the Oracle series as a midquel to the two.
- The Legend of Zelda: Majora's Mask has the Link from The Legend of Zelda: Ocarina of Time, going to Termina. The game's working title was Zelda Gaiden. It was supposed to be an add-on of sorts using the 64DD peripheral.
- The Legend of Zelda: Phantom Hourglass is a side-game/sequel to The Legend of Zelda: The Wind Waker.
- The Four Swords trilogy was supposed to be made up of these, and then Four Swords Adventures shoehorned Ganon into the plot and connected it to the main series.
- A good example for Twilight Princess is Link's Crossbow Training for the Wii.
- Freshly-Picked Tingle's Rosy Rupeeland is either this or a spinoff.
- The Yakuza series has Dead Souls, which, as opposed to the main games which feature crime drama stories and brutal hand-to-hand fighting gameplay, takes place in the midst of a Zombie Apocalypse and prominently features gunplay.
- The original Ninja Gaiden trilogy for the NES, along with the arcade game released alongside the first NES installment, weren't actually side-stories to anything. In Japan, the series was originally known as Ninja Ryūkenden (Ninja Dragon Sword Legend). The use of "gaiden" in the English version is an example of Gratuitous Japanese, since the developers were not sure how to localize the Japanese title ("Ninja Dragon" was considered one point, but Data East beat them to it with their beat-'em-up Bad Dudes vs. Dragon Ninja, and a literal translation was considered to be too long). With that cleared up, Ninja Gaiden Dragon Sword could be considered one to the Xbox series.
- When Koji Igarashi took over as producer of the Castlevania games (starting with 2002's Castlevania: Harmony of Dissonance), he declared that the Nintendo 64 games ( Castlevania 64 and its Updated Re-release Castlevania: Legacy of Darkness), and Castlevania: Circle of the Moon for the Game Boy Advance were side-stories to the main Castlevania storyline. The Game Boy game Castlevania Legends on the other hand, is no longer part of the canon.
- In Japan, Castlevania: Legacy of Darkness was titled Akumajō Dracula Mokushiroku Gaiden: Legend of Cornell, making it a Gaiden Game to the earlier N64 title, whose Japanese title was Akumajō Dracula Mokushiroku.
- The Boku Dracula-kun games for the Famicom and Game Boy (the latter brought over to the U.S. as Kid Dracula) were never intended to be canon, though the Big Bad, Galamoth, would later appear in the regular series.
- While not directly linked to another game, Indiana Jones and the Fate of Atlantis could be considered a Gaiden Game to the Indiana Jones series of movies.
- Resident Evil
- Resident Evil Gaiden was the actual name of the game. Its ending has since been decanonized without doubt.
- The light gun Spin Offs could also count, though they have slightly more credible ties to the Canon. Some even seem to be retcon vehicles.
- Resident Evil 3: Nemesis may be considered a gaiden to the second game.
- Destroy All Humans! Big Willy Unleashed is a Gaiden Game in the Destroy All Humans! series.
- Devil May Cry 2 is a two-disc set. The second disk, which you may think will extend the story, doesn't. It fits this trope by giving you a gaiden game in form of Lucia, letting you play as her for the parts of the story where she wasn't interacting with Dante. It makes little enough sense what she's doing that it could easily be considered a wholly different game played in the DMC format.
- The Gundam anime franchise has quite a few Gaiden Games, most of which are spinoffs of the original series and depict events that take place at the same time as White Base's adventures but in different parts of the world. The best-known of these include Rise from the Ashes (set in Australia), Blue Destiny (set in North America), and more recently Gundam 0081 (which takes place between the original series and Gundam 0083). Some other games shift between this and a full-on Licensed Game - Zeonic Front and Federation vs. Zeon on PlayStation 2 alternate between missions totally separated from the events of the anime and missions that put you right in the middle of major battles from the anime.
- Melty Blood, the rather popular 2D Fighter Gaiden Game to Tsukihime, which follows a plotline that didn't quite make it into the actual visual novel.
- Subverted when it basically became it's own series.
- After the original Guilty Gear, X and X2 are sidestories like the drama cds. The main plot is now in Guilty Gear 2: Overture. (Don't worry, Word of God still says it's canon...mostly...especially with the release of Accent Core plus...which seems to tell the story on how they got to Overture.)
- Soul Calibur 2's Weapon Master Mode appears to be a gaiden storyline: Weapon Master Mode takes place...somewhere other than Europe and Asia. Also, none of the Soul Calibur characters appear in Weapon Master Mode; the characters in Weapon Master Mode use the Soul Calibur fighters as "avatars", i.e. you're not actually fighting Mitsurugi, you're fighting some guy named Edgar. Although there is a Lizardman named Calcos, aka Aeon Calcos who was transformed into Lizardman in the first Soul Calibur. Boy is this complicated.
- Weapon Master Mode is definitively a gaiden, likely not related to the main plot (thought there are a few hints of it being a tale from the distant past, like Tristy's final words, which seems to hint that either him or the player is Edge Master; and the existence of Arcturus, Algol's son from 4. Oh, and the Calcos lizardman was just a Continuity Nod, not meant to be the one in the main games.
- In Soul Calibur 3, it was a Euro-Asian conflict, by chance, happened to be in the areas where the characters looking for Soul Edge. The king you worked for had it all along, and is batshit insane.
- Chronicles of the Sword is an Alternate Universe, set on a ficticious continent with ficticious countries, and starring the Soul cast as mere cameos with no storyline relevance. It's not part of the main canon.
- Mortal Kombat's action games: MK Mythologies: Sub-Zero, MK: Special Forces (starring Jax), and the more recent MK: Shaolin Monks with Liu Kang and Kung Lao.
- Also the Konquest Mode from MK: Deception, which starts 50 years before the main game's story and ends in the beginning of Deception, and shows the story of one of the characters' exploits while unknowingly serving the Big Bad's personal agenda.
- The first Street Fighter EX originally had the Working Title Street Fighter Gaiden and the plot of the EX series (what little it has) is considered a side-story to Street Fighter II.
- Despite being a small series (in terms of the number of entries, at least), Punch-Out!! has one of these: Arm Wrestling. It used the same two-screen arcade cabinet style of the original 2 games, its art style was similar to the Punch-Out!! series at the time, the main character resembled the arcade version of Little Mac (who had green hair), and arm wrestler Mask X, once his titular mask is removed, is revealed to be Bald Bull.
First Person Shooter
- Unreal Tournament is a Gaiden Series to the Unreal series, taking place within the Unreal universe but having little to do with the Skaarj invasion.
- And the Unreal Championship games for consoles are a spinoff from Unreal Tournament, creating a Gaiden Game of a Gaiden Game.
- Unreal Tournament III could be considered a Gaiden Game for the rest of the UT games - it still plays like they do, but it actually has a storyline beyond "become the Champion" and as such might be the closest we'll have to an actual Unreal 3.
- Another gaiden game of sorts is Halo 3: ODST; despite that 3 in the title (and being based off the third game's engine), it actually takes place during Halo 2, and involves an almost totally different cast of characters.
- The reason why ODST has a 3 in its title is because it was originally planned to be merely an add-on that still required Halo 3 to play. But as the game grew and grew and more and more tweaks to the game engine were made note , Bungie decided to make it a stand-alone product for half the price of a normal retail game. Then Microsoft "interfered" and added a second disk containing the multiplayer portion from Halo 3 along with all the DLC map packs, and upped the price to that of a normal retail game.
- Halo: Reach is a side story prequel to Halo: Combat Evolved that takes place concurrently with the latter parts of Halo: The Fall of Reach.
- Most of Medal of Honor: Frontline, except for the D-Day prologue, is set in between the third and fourth missions of the original game. Allied Assault also has a few continuity nods to that.
- Call of Duty 4: Modern Warfare for the Nintendo DS, in relation to the versions released on Xbox 360, PC, and PS3. The game features similar missions, but featuring characters from other teams operating either in parallel or in support of the teams from the main release. Every "main" release in the series has since been followed by a handheld, mobile, and/or, in one case, last-gen version that acts as a side-story to the main game; the aforementioned last-gen version, for World at War, is notable in that it and the DS version both included a British campaign like every other World War II-based game in the series had, whereas the 360, PS3, and PC version had its British campaign and associated assets cut.
- The second Expansion Pack for First Encounter Assault Recon is this for both the original game and its first expansion pack, starting within the last hour or so of the original game and ending before the first expansion does.
- Metroid Prime: Hunters is connected to the Prime trilogy since it takes place between Metroid Prime 1 and 2, but that's where the connections end. While the Prime series focuses on recurring element, Phazon, Hunters does not use or reference Phazon at all, but the story focuses on Samus and a bunch of other bounty hunters all fighting each other for a rumored absolute power contained somewhere in the galaxy. The game focuses a lot more on the online multiplayer as well, whereas the Prime trilogy only used multiplayer once (local, no online) and it was a side thing instead of a main attraction.
- Since Other M's release, the creator of the series has said he considers the Prime trilogy in general to be this.
- The irony is that Other M itself can also be easily labeled as a gaiden game, due to the fact that it's structured and presented radically different from any other game in the series and serves as a bizarre prequel of sorts to an earlier game that was perfectly understandable by itself.
- Since Other M's release, the creator of the series has said he considers the Prime trilogy in general to be this.
- Players of DUST 514 take the role of ground-based mercenaries in the EVE Online universe. EVE players can hire Dust players to seize or defend planetary facilities for them, and provide airstrikes
- Though chronologically a sequel, Bioshock 2 qualifies as the game is from the perspective of a Big Daddy, specifically a prototype named Delta. The gameplay is similar, but the mechanics and weaponry are modified slightly to give the feel of controlling one, and you also have a relationship with Little Sisters similar to that of the Big Daddies themselves. The storyline also give some additional insight into the concept and technology of the Big Daddies as well.
- There's a couple in the Sonic the Hedgehog series. Tails Adventure springs to mind. In the Japanese manual its said to take place before Tails' fateful meeting with his iconic partner in crime fighting. In the Western version it's treated as a Bus Mans Holiday but in both, its still Tails's day in the limelight.
- Each Donkey Kong Country game had a Game Boy follow-up in the "Donkey Kong Land" series. The first was a completely separate adventure, the second was basically a port of Donkey Kong Country 2 and the third was a basic collection of very generic levels in the style of Donkey Kong Country 3.
- Daxter takes place before the main events of Jak II: Renegade. The game is A Day in the Limelight for the sidekick, Daxter, without Jak having a playable role.
- Ratchet & Clank: Size Matters and Secret Agent Clank have their settings unconfirmed, but known to be after the third game. However, their canon status is disrupted, and are completely ignored by Insomniac Games.
- Portal is almost an inverted example; everything (bar a couple of throwaway references to Black Mesa) was original, and the connections to the Half-Life story were made in the main Half-Life series.
- Blue Shift, Opposing Force and Decay could probably also be considered Gaiden Games. Especially Opposing Force, which while set in the same time-frame as the original, introduced new aliens (Race X) and characters (Cpl. Adrian Shepard, Security guard Otis Laurey) that have not been considered "canonical" by Valve.
- Trilby: The Art of Theft is Yahtzee's Gaiden Game for the Chzo Mythos series, featuring as it does one of the main characters years before the series proper starts, and an Unexpected Gameplay Change to stealth platforming.
- Back in the 1990's many PC and Amiga titles were made into a Christmas Special Gaiden Game, usually released in some gaming magazine's cover disk as a present for fans. The games that got this treatment included Cannon Fodder, Dizzy, Fire and Ice (coverdisk for the Christmas 1992 issue of Amiga Power), Lemmings and Jazz Jackrabbit (the latter of which actually got two separate Christmas editions, the 1994 "Xmas Edition" and the 1995 "Holiday Hare"). This also happened in the 1980s with Moley Christmas, a Monty Mole game exclusively distributed with a ZX Spectrum magazine with a self-referential plot.
- Gargoyle's Quest has the Japanese title Red Arremer: Makaimura Gaiden; it is a spinoff of Ghosts N Goblins, or Makaimura in Japan.
- Shift Freedom, which has the same mechanic as the main Shift series, but does not appear to be part of that story.
- Super Mario Land and Super Mario Land 2 share the same basic platforming elements like Super Mario Bros., but take some liberties with the story, settings and items. Instead of rescuing Peach from Bowser like usual, Mario takes a trip to a neighbour country of the Mushroom Kingdom to save a different princess from an evil alien in the first game. In the sequel, Mario has to take back his private island from his evil counterpart, Wario. The third game distances itself completely from Mario and gives birth to the Wario Land series instead. Notably, none of the games were designed by Shigeru Miyamoto, but were well-received nonetheless.
- The DJ MAX series has primarily been a beatmania-like game, but the newly-released arcade game DJ MAX Technika is a much different game, with touchscreen-based gameplay combining elements of Osu! Tatakae! Ouendan/Elite Beat Agents and Lumines. Due to its similarities to the former and its harsh Life Meter, it's a very Nintendo Hard game; you can easily fail a song in the first 10 seconds.
Real Time Strategy
- Halo Wars is a Real-Time Strategy spin-off/prequel to the main Halo series.
- Yggdra Unison is a gaiden game to Yggdra Union; it allows the player to command any army, make any alliances he or she wants, and aim for world domination in a Wide Open Sandbox style of play. The game is considerably more lighthearted than its canon counterpart, and concentrates on character development and interaction over story.
- Shin Megami Tensei If started off originally as a gaiden game of sorts in the Shin Megami Tensei universe, taking place just before Shin Megami Tensei I. It later became canon when the protagonist appeared in Persona and Persona 2, and started the Inter Continuity Crossover that occurs throughout the Megaten franchise.
- Shin Megami Tensei: Strange Journey may sort of count; despite the fact that it was originally meant to be the fourth game in the main series, it doesn't have a clear-cut connection with the previous three entries (which themselves were pretty closely linked together).
- Hell, it turns out that the actual Shin Megami Tensei IV isn't all that connected to the other main series games either.
- There are more spinoff games than there are main series games. Hell, there are more games in the Persona series than in the main series.
- There are even Persona spinoffs (a spinoff of a spinoff,) including fighting game Persona 4 Arena (which might not count, as it advances the plot of the series, even if only a little bit) a browser-based RPG, and a long series of cell phone games based on Persona 3 (including one focusing on Aigis 10 years before the start of the game.)
- Shin Megami Tensei: Strange Journey may sort of count; despite the fact that it was originally meant to be the fourth game in the main series, it doesn't have a clear-cut connection with the previous three entries (which themselves were pretty closely linked together).
- Sailor Moon: Another Story was not so much a franchise distancer as a nod that it is not canonical to the Sailor Moon mythos in very Broad Strokes.
- Final Fantasy X-2 orginally was informally referred to as a Gaiden Game before being treated as a direct sequel. Largely existing as an exercise in producing a sequel and light-hearted enough to occasionally take the piss out of its premise and characters, it was mainly dismissed in the West for being much sillier than its predecessor, and for deviating too much from the Final Fantasy formula.
- Even before X-2, the developers weren't sure if Final Fantasy IX would be considered part of the main franchise due to how much is deviated from Final Fantasy VII and Final Fantasy VIII; it was less than a year before release that Square officially called it IX.
- The spinoff games to the VII universe could be considered Gaiden Games, including the PS2 sequel Dirge of Cerberus, and two prequels, Before Crisis for mobile phones and Crisis Core on the PSP. Fans are divided how much material has been stapled on as a cash grab and how much was simply cut for time.
- Galaxy Angel EX is a non-canonical glorified giant minigame.
- It could be argued that Xenosaga 2 and 3 were Gaiden Games, not to Xenosaga, but rather to Xenogears. There's a lot of legal difficulties in the connections between those, so just look at the Xenosaga article on The Other Wiki to learn more about the connections (and lack thereof).
- Phantasy Star Gaiden was originally intended to fill in some side events to the series to act as the lead-in to an earlier concept for Phantasy Star 4. As that game ended up using a different storyline in the final version, and there hasn't been a single game released in that continuity since, said Gaiden is now meaningless to the overall continuity.
- Many gaidens are found in the Mega Man franchise — in fact, each series seems to get at least one. Typical examples are Mega Man & Bass, Mega Man X: Command Mission, Mega Man Legends and The Misadventures of Tron Bonne, and Mega Man Battle Network: Battle Chip Challenge.
- The first two Shining Force Gaiden games (Game Gear) were eventually bundled under the name Shining Force CD (Sega CD). And just to be confusing, Shining Force Gaiden III: Final Conflict is unrelated to the previous two Gaidens (aside from being on Game Gear) and is instead a bridge taking place between the first two 'proper' Shining Force games.
- The handheld titles of the Kingdom Hearts series are frequently considered Gaiden Games to the "main" series, perhaps because of their tendency towards Word Salad Titles and the fact that they're on handhelds, rather than consoles. This is not the case; these games are all full installments of the series which build upon the story of the games and lead directly into the next "main" game. Kingdom Hearts II makes more sense if you've played Chain of Memories and the games released after Kingdom Hearts II are quite clearly building up to a climax that will be resolved in the future Kingdom Hearts III.
- The GBA remake of Final Fantasy II contained a short quest after beating the game, detailing what happened to all the dead party members after they died.
- Super Robot Wars has three Gaiden games with each of them a part of the three major continuties ("Classic", Alpha, and Original Generation). The first Gaiden game Super Robot Wars Gaiden: Lord of Elementals told of the origins of the Masou Kishin characters, a group of Banpresto-created originals not seen anywhere else. Super Robot Wars Alpha Gaiden focused on Time Travel and wasn't necessary for players to enjoy the previous Alpha game (most likely because Banpresto wanted an excuse to show off obscure mecha series, since it was full of them). Super Robot Wars Original Generation Gaiden fits this trope because it was shorter than the average SRW, including several extras such as a battle viewer and a card game. It's also downplayed, though, since all three are essentially sequels that happen to have the word "gaiden" in their name. Super Robot Wars Alpha depends on the player having some foreknowledge of the events set in Super Robot Wars EX or Super Robot Wars Gaiden for background on the Masou Kishin characters, otherwise one can get too confused at the references they make to Alpha's back story. Alpha Gaiden is heavily referenced in the proper sequel Alpha 2, where the Dinosaur Empire is defeated for the third time, and the finale Alpha 3 assumes the player knows of Sanger Zonvolt's role at the Earth Cradle, despite the fact it was supposed to be highly secretive. Hell, the fact the Titans are more or less liberally screwed and Char Anzable's disillusionment with humanity DEPENDS on the events of Alpha Gaiden. In short, Banpresto's definition of "gaiden" means a game that provides story details bridging the gap and answering the Epileptic Trees present in the other games in continuity. In fact, there's very little an "Original Generation 3" couldn't reference the events of Original Generation Gaiden, considering both the effects on existing characters and all the EarlyBirdCameoes present in that game.
- A better example is Super Robot Wars OG Saga: Endless Frontier. While a spin-off, the back-story establishes the events in Original Generation continuity ultimately influenced the entirety of Endless Frontier. Its sequel Endless Frontier EXCEED even manages to rope in characters from the main Original Generation games.
- Amusingly, a remake of the original Super Robot Wars Gaiden has been announced, only it now carries the "OG Saga" subtitle instead. Thus, the name "Gaiden" has become reserved for half-sequels while "OG Saga" is given to the actual Gaiden Games.
- Chrono Cross is somewhat of a Gaiden Game for Chrono Trigger, being set 10 years after the "present" time in the latter and retaining only a handful of characters, all of whom show up in three scenes or fewer. What really makes it gaiden, though, is the fact that, in the end, the entire point of the story is to resolve a hanging plot thread from its predecessor (see Urban Legend of Zelda).
- Radical Dreamers was a Japan-only text adventure Gaiden Game to Chrono Trigger released on the SNES' Satellaview addon. It was later overhauled, greatly expanded, turned into a proper RPG... and became Chrono Cross.
- The Worlds of Ultima series were Gaiden Game's taking the fantasy-based Ultima VI engine (and main character) to other settings, such as Mars. Ultima Underworld was also a Gaiden Game, being a side story set in the main Ultima world, because its plot directly bridged Ultima VII and Ultima VII Part 2 (in fact, in the latter the PC starts with a quest item obtained in UU2 with no in-game explanation of where it came from).
- The two console games from the mid 90s, Ultima: Runes of Virtue and Ultima: ROV 2, would certainly count as well. Both games are set in the usual Ultima game world, and feature characters and towns familiar from the parent series. But both games are more like action games than RPGs, and neither one is part of the official Ultima chronology. They are, like Underworld, a separate mini-series of their own.
- There are two Japan-only games in the Suikoden series called, quite simply, Suikogaiden volumes 1 and 2. These games are basically side-stories featuring a previously-unknown character from Harmonia named Nash Latkje (who would later appear as a Star of Destiny in Suikoden III). The two games take place around the time of Suikoden II, the first starting before and during SII, and the second taking place shortly after the end of SII. In both games, Nash interacts with various characters from Suikoden II, giving more perspective on many of the lesser-known characters.
- The Elder Scrolls had an action-RPG, An Elder Scrolls Legend: Battlespire, and an action-adventure, The Elder Scrolls Adventures: Redguard (another Elder Scrolls Adventures, The Eye of Argonia, was planned but never made, though the Eye itself is mentioned in the main games). (Those who don't know this often erroneously assume that it's a reference to The Eye of Argon.) There's also the Elder Scrolls Travels side-series, consisting of Dawnstar, Stormhold, and the mostly not-canon Shadowkey, for the ill-fated N-Gage system. Finally, The Elder Scrolls Online will be an MMORPG set several hundred years, minimum, earlier than Arena.
- The Deus Ex Game Mod Zodiac has JC Denton's brother Paul Denton investigate a separate conspiracy.
- The Enhanced Edition of The Witcher has two additional stories named 'Side Effects' and 'The Price of Neutrality', which are completely unrelated to the main game, but feature locations and characters known from there.
- Barkley, Shut Up and Jam: Gaiden: A spinoff RPG from the original sports game Barkley: Shut up and Jam! There's also that Space Jam is also part of the game's canon.
- Pokémon has had a bunch of side games. An incomplete list: the First Person Snapshooter game Pokémon Snap; the Puzzle Game Pokemon Trozei!; and the Pokemon Mystery Dungeon and Pokemon Ranger series. Likewise, the main series games are all Gaiden Games of each other, with references and allusions but no actual interaction. Mystery Dungeon & Ranger also have references and allusions but no interactions to their own series', so gaiden games that are gaiden games of each other...
- Breath of Fire IV has had a minor constellation of Gaiden Game treatments—at least two of them being released (along with a Comic Book Adaptation of IV) fully seven years after the original release. These last two, Breath of Fire IV - The Sword of Flame & the Magic of Wind and Breath of Fire IV: Faeries Light Key, are two separate side-stories of IV. There's also a spinoff of the fishing minigame from IV as well as a "Great Dalmuti"/"Millionaire" game featuring characters from IV. Unfortunately, due to the platform these were released on (Qualcomm's BREW OS, which is only common in Japan) these are likely to remain No Export for You permanently—much to the vexation of the English-speaking IV fandom.
- The Front Mission spin-off Gun Hazard is not only a side-scrolling shooter, but also takes place in its own alternate universe.
- NieR is one of Drakengard, with the former taking place after the most bizarre ending of the latter (Caim and Angelus chase an Eldritch Abomination into modern day Tokyo and and after defeating it are blown to hell by fighter jets).
- Not only that, but Drakengard's joke ending becomes very serious for Nier. Caim, Angelus, and their quarry brought magic into the real world... and magical diseases like White Chlorination Syndrome against which a world without magic had no defense...
- Valkyria Chronicles III is a Gaiden Game to the original Valkyria Chronicles. It takes place during the same time frame from the perspective of a different unit in the same army as the original game's protagonists.
- Fallout: New Vegas is an odd case of a Gaiden Game that is more of a sequel to its predecessor (Fallout 2) than the actual sequel is: 3 was made by a different developer (Bethesda) than Black Isle, the developers of the first two, and moved the setting to the opposite end of the country. New Vegas's developer (Obsidian) had many key members in common with Black Isle, takes place closer to familiar ground, and incorporates many elements from the cancelled Van Buren project that was originally going to be Fallout 3.
- Additionally, most of the add-ons for 3 and New Vegas have a separate map from the main game, as well as a self-contained story.
- The Ogre Battle series has two. Ogre Battle: Legend Of The Zenobia Prince, a Japanese-only game for the Neo Geo Pocket and Tactics Ogre: The Knight of Lodis, both of which tell the backstories of characters from Ogre Battle and Tactics Ogre, respectively.
- The World of Mana series has a number of titles not in the main series — Legend of Mana, Children Of Mana, and Heroes of Mana. But what's more interesting is that the original game, released as Final Fantasy Adventure in the US....was actually called Seiken Desnsetsu: Final Fantasy Gaiden (and was in fact the first game in the US to have a Chocobo in it!).
- Dragon Age: Origins has a couple DLC missions that don't star the Grey Warden: Leiliana's Song, which explains how the secretive nun came to Ferelden, and Darkspawn Chronicles, a What If? where the Warden didn't survive the joining and the Darkspawn won the war.
- Baldur's Gate had Tales of the Sword Coast, an expansion for the first game that added three new optional dungeons that had nothing to do with the main story.
- Lufia The Ruins Of Lore is one to the Lufia series, dealing with a subplot from Lufia II: Rise of the Sinistrals rather than the overarching plot of the rest of the series. Even its Japanese name is Estpolis Gaiden.
- Gradius Gaiden, the only Gradius title that allows the player to rearrange the power meter, and the second non-Parodius game to have multiple selectable ships (the MSX title Nemesis 3 being the first). And for that matter, the MSX version of Salamander, and MSX exclusives Nemesis 2 and 3. The MSX Salamander plays more like a Gradius title, and has several new features such as a powerup that temporarily stops the screen scrolling. Nemesis 2 is an original title with the ability to fly into about-to-be-destroyed boss ships and obtain new powerups such as an upward-firing laser, at the cost of having a longer power meter. Nemesis 3 is a retelling of the more mainstram Gradius II: Gofer no Yabou with Nemesis 2-style gameplay. Also, the Salamander series is a gaiden series to Gradius.
- R-Type Leo has gameplay significant from a "real" R-Type game. Instead of a Force Pod, you had two smaller pods that provided additional firepower and had a homing charge attack, and the plot takes place before any other games in the series. The obscure Armed Police Unit Gallop is also a Gaiden Game.
- The numbering of the four * .5 games (Immaterial and Missing Power, Shoot the Bullet, Scarlet Weather Rhapsody and Double Spoiler) would imply that they're all gaiden games to the main Touhou series (Touhou 12.3, Hisoutensoku, is an Expansion Pack to SWR), especially since none of them use the same gameplay system (IaMP and SWR are both 2D Fighting Games, and StB and DS are Boss Rushes where you take pictures instead of fighting back). However, of the four, StB and DS are the only ones without an actual plot — whereas the events and new character introduced in IaMP are acknowledged in the canon books Perfect Memento in Strict Sense, Bohemian Archive in Japanese Red, and Silent Sinner in Blue (SWR was made after those books came out).
- IaMP boss character Suika Ibuki appears in Subterranean Animism, and the game actually elaborates on some of IaMP's plot (that is, where the oni all went). Iku Nagae and Tenshi Hinanai from SWR are both in The Grimoire of Marisa. The newest Gaiden Game, Touhou 12.8 Great Fairy Wars, is a direct continuation to a chapter of a Touhou manga, Strange and Bright Nature Deity. Basically, Touhou is undergoing Continuity Creep.
- Metal Slug had a canon gaiden game on the Game Boy Advance, detailing a new training facility that was overrun by Morden's forces. Best of all, two of the trainees, playable characters Walter and Tyra, single-handedly take it all back.
- Time Crisis: Project Titan, Crisis Zone, and Razing Storm.
- To clarify, Project Titan was a PSX-only sequel starring Richard Miller. It most definitely took place after 1 (note Wild Dog's mechanical arm); how long is uncertain. It doesn't affect anything that happens afterward, so it's no surprise you don't hear about it. Crisis Zone and Razing Storm are unrelated games which use the TC 2-and-later engine.
- Darius has its own gaiden game in the form of Syvalion. You even have a Silver Hawk fly along side you in one stage and the metal dragon cameos in Darius Burst.
- Epic Battle Fantasy does this in a similar way to the Touhou examples above- and inverts it. How does it invert it? 1, 2, and 3 are basically RPG games. EBF 3.3: Bullet Heaven is a Bullet Hell game.
- Aleste Gaiden, in contrast to other Aleste games, has the hero running and jumping in Powered Armor and a relatively limited weapon selection. The ending reveals that it takes place in Another Dimension from the original Aleste, with the same protagonist and villain.
- Halo: Spartan Assault is a side-story interquel which takes place between Halo 3 and Halo 4.
- Colony Wars III: Red Sun feels like this in comparison to its two predecessors. The main character is a neutral bounty hunter with no ties to either of the main factions, it takes place concurently with Vengeance rather than after it and the League/Navy conflict is mostly in the background, with most of the missions instead involving feuds between newly-introduced factions and the protagonist investigating an outside threat.
- Warhammer and Warhammer 40,000 each have a number of spinoff tabletop games in their universes. Warhammer Fantasy's games include Warhammer Fantasy Roleplay, the gang-based Mordheim, American football parody Blood Bowl (even referring to the mystical god 'Nuffle'), the naval fleet based game Man O'War and massive-battle Warmaster. 40k has the large-scale "narrative wargame" Inquisitor, space combat Battlefleet Gothic, small-scale Epic, all-Ork Gorkamorka, air-battle Aeronautica Imperialis, gang-based Necromunda and recently the role-playing game Dark Heresy.
- Dawn of War was originally supposed to be this, creating an all-new Space Marine chapter, the Blood Ravens, to avoid stepping on continuity's toes. The fans liked them so much that Games Workshop went ahead and canonized them, the games, and the events therein.
- There is also Path To Glory for fantasy which you play as an aspiring champion of chaos.
- Also there is Kill Team for 40k note that has a small team of elite units infiltrating and completing a objective.
Third Person Shooter
- The Mass Effect series has had multiple examples of this:
- Mass Effect: Galaxy (for the iPod Touch/iPhone) focuses on Jacob Taylor and Miranda Lawson between the events of the first and second game. Completing Galaxy unlocks more dialogue in Mass Effect 2.
- The iOS game Mass Effect: Infiltrator runs concurrently with the events of Mass Effect 3, and follows an ex-Cerberus operative who works to free a number of captive civilians from Cerberus' laboratories. The game has similar mechanics to the main game, and completing it allows the player to export a War Asset and a weapon over to 3.
- Mass Effect: Datapad is another iOS game integrated with the third installment, and includes a galactic Codex, the ability to receive personal messages from squadmates and various characters in the universe, and a strategy minigame that allows you to increase your Galactic Readiness in the main game.
Turn Based Strategy
- Because Everything's Better with Penguins, Turn-Based Strategy series Disgaea has a platformer spin-off for the PSP called Prinny: Can I Really Be the Hero? starring everyone's favorite explosive waterfowl squad.
- FunOrb's "Armies of Gielinor" is a Turn-Based Strategy based on the history of the world of Runescape.
- The aptly named Fire Emblem Gaiden is a side-story to the original Fire Emblem game, while Fire Emblem: Thracia 776 is one to Genealogy of Holy War. The two titles are generally considered full instalments in the Fire Emblem series, being the second and fifth respectively, though there are some portions of the Japanese fanbase who don't consider Gaiden to be a full FE game. Also present are the Satellaview instalments in the series, which are briefer games focusing on small groups of the cast of the first/third game doing things in the intervening time period between Dolhr's victory and the start of the first/third games; they were later remade and included as a bonus in New Mystery of the Emblem.
- Phoenix Wright: Ace Attorney's bonus case, only present on the DS version (The original Japan-only GBA version ends at the fourth case), features a case where only 5 characters (Phoenix, Edgeworth, Gumshoe, the Judge and the Bellboy) from the rest of the series appear, the rest being completely new. This is due to the case taking place between the first and second games, and the writers couldn't mess with the continuity already set by the sequels which had already been released in Japan. The plot and characters feel perfectly like a sidestory.
- The fifth case has been worked into the Canon with Apollo Justice: Ace Attorney featuring Ema as the game's Gumshoe.
- Gyakuten Kenji (or Ace Attorney Investigations: Miles Edgeworth), a Gaiden Game where you play as Miles Edgeworth, Nick's rival. It follows the same general formula except that Edgeworth is actully on the map as a sprite and walks around rather then looking at a static image. There is no court segments (Unless the case taking place in a court house counts), but witnesses are still cross examined in much the same manner as the main series. It now has its own sequel, becoming a Gaiden Series.
- Higurashi Daybreak, a doujin game for Higurashi no Naku Koro ni that's literally become a canon side story.
- There's also Jan, in which the characters can (depending on the mode) go crazy and kill each other just like usual, and they're dueling with... mah-jong?
- Similarly, Umineko no Naku Koro ni will soon have its own Gaiden Game in the form of Umineko No Naku Koro Ni - Tsubasa, and will contain all the side stories released beforehand.
- CLANNAD: Tomoyo After: It's a Wonderful Life.
- Kud Wafter is this to Little Busters!.