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Video Game / Mega Man Battle Network 4: Red Sun and Blue Moon

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Mega Man Battle Network 4 is a video game created by Capcom for the Game Boy Advance in 2003. It's the fourth installment in the Mega Man Battle Network series. There are two versions: Red Sun and Blue Moon.

Five months after the previous game, Lan now goes to 6th grade, but evil is still on the loose, as a new threat lurks to cause chaos, so Lan and MegaMan.EXE must defeat it. At the same time, they participate in multiple NetBattle tournaments, all the while an asteroid is quickly heading to Earth.

Battle Network 4 is unique in the series for its structure. The three tournaments Lan and MegaMan enter have semi-randomized opponents, with each one having their own small story scenario between matches. This makes each playthrough different and encourages entering New Game+ (also unique to this game) twice to see everything and achieve 100% Completion.


Additionally, the big new gameplay mechanic in this entry is Double Soul, replacing Style Change. By sacrificing a battle chip, MegaMan takes on the abilities of another Navi he's resonated with for three turns. Double Soul replaces the Mega Buster's charge shot and provides other abilities, such as boosting damage for specific battle chips. There are six Double Souls in each version and only three can be obtained in the first run, making the mechanic the biggest motivator for replaying the game.


This game provides examples of:

  • A.I. Breaker: ProtoMan is infamously vulnerable in the first encounter with him, as he only uses one attack from a specific position. Using an Area Grab will leave him helpless for the entire match. KendoMan is also known for having very flawed programming, even during his upgraded fights.
  • Anti-Frustration Features: There are a couple of instances where there are no penalties for using Dark Chips:
    • At one point in the story, the player is forced to use a Dark Chip to defeat ShadeMan.EXE, who is immune to everything else. All Dark Chip penalties are disabled in this event, as it would have otherwise applied more Maximum HP Reduction with every gameplay loop.
    • Speaking of ShadeMan.EXE, his Bonus Boss appearances do not have his invincibility in effect (though he will still Teleport Spam out of attacks occasionally).
    • If one player is thrashing the other player a little too hard in a Link Battle, Dark Chips become a more proper Desperation Attack as Link Battles do not affect karma or maximum HP — but the Dark Chips will still apply their mid-combat debuffs!
  • Artificial Stupidity: Enemy Navis on the first playthrough are slower, weaker, and in some cases use less attacks than they did in previous installments. ProtoMan in particular was downgraded viciously from his previous Perfect-Play A.I. strategy, leading to the AI Breaker listed above.
  • Art-Shifted Sequel: This game's overworld uses smaller sprites and more saturated colors with the portraits more closely resembling the official art and the anime; this look carries over to the rest of the series. Downplayed with the battle sprites, which sees a much more subtle shift to brighter, simpler colors.
  • Awesome, but Impractical: Dark Chips are attacks equivalent to Program Advances in power that appear when the player is performing badly. If one uses them enough, MegaMan will gain access to them by default and certain Evil Chips will be usable. The problem is that the drawbacks far outweigh the benefits: Maximum HP Reduction, status ailments depending on the Dark Chips slotted in (not used, just taken from the menu at all), being unable to use Full Synchro, Soul Unisons and most Mega Chips and the HubBatch becoming unavailable at the end of the Bonus Dungeon. Worse, Dark Chips are outright disabled against the difficult final boss. In contrast, simply playing well and refusing the Dark Chips raises a chance to score double damage on any hit — a perk so powerful it was removed from the sequel.
  • Bag of Spilling: MegaMan has been reset to effectively level 1 yet again, on top of losing the ability to Style Change. This is because his deletion and subsequent restoration at the end of the last game led to data being lost, such the Change.bat file required to Style Change. The Navi Customizer is also not available initially, but that's because it was confiscated by Haruka to keep her kids out of trouble.
  • "Blind Idiot" Translation: Those two games have more translation messups and typos than any other installment in the series. For example, the new bad guy class of Heel navis is mistranslated as "Heal" navis, and the game is absolutely insistent on the specific phrase "viruses bust" for referring to the eponymous activity, even when it makes no grammatical sense (and it never does). Even the text formatting in the dialogue boxes is awkward.
    • "What a polite young man she was", regarding Lilly.
    • "Mega Man, is the jack out now!"
    • "There are so many electronic store!"
    • "Leg's go, Mega Man!"
    • "Want to saver you progress?"
    • "It's Phone!"
    • Many battlechips in the game have nonsensical and confusing descriptions, even accounting for the little space available for text.
    • The manual was also a mess.
  • Bound and Gagged: Lan's doghouse alarm goes off and he rushes home to find his mother tied up and gagged on the floor in the corner of his room and warned him that they could easily do worse.
  • Brick Break: In Blue Moon, Tamako attempts this on a large rock (and hurts herself somewhat) to drive a point regarding "fighting spirit" with Lan. She will refer MegaMan to a Cyberworld fighting master who has him break three of them within a short time limit, then challenges him to three rounds of this against MetalMan before the tournament battle.
  • Broken Aesop:
    • During the first tournament's prelims, Lan and MegaMan defend the Hidden Mettaur Village from a HeelNavi on the grounds that they "weren't doing anything wrong." However, in Match's scenario, they discover a virus in a malfunctioning grill, immediately assume it's causing problems, and delete it; they later learn that the virus was installed by Mr. Match to run the grill in the first place. Mr. Match argues that even viruses have their place, but Lan disagrees.note  While this could stem from Lan's suspicion towards Mr. Match after the FlameMan incident nearly cost his father's life in 3, him not mentioning said event cancels that reason somewhat.
    • Also in the game, during the TopMan chapter, Lan discovers that NetBattling isn't merely "a game for the young" when they discover their opponent is a senior citizen. In the ColdMan Scenario, however, Ivan Chillski calls NetBattling "just a game", which causes Lan to blow a gasket and threaten to physically attack him.
    • While the game assumes you don't (and for good reason), using dark chips essentially invalidates its message in the finale. Sure, MegaMan can't use dark chips against Duo and beat his dark side, but he still has the evil portrait, can't use light chips or Doublesoul, and can still use dark-aligned chips like Static.
  • But Thou Must!: You're forced to use Dark Chips to defeat ShadeMan during his second fight, as he's immune to all other forms of damage.
  • Cash Gate: Expect to shell out money for things like passcodes, C-Slider parts and chips with specific codes that cannot be obtained outside from Chip Traders in order to progress through the story. Becomes very painful in the first playthrough, where the payouts from battles and Mystery Datas are ridiculously small compared to how much and how frequently the NPCs demand Zenny from the player.
  • Continuity Nod: These games are saturated with throwbacks to earlier games in the series.
    • Lan's introduction directly mirrors his intro from the first game, up to and including having to collect his PET from across the room after Mega wakes him up.
    • The tutorial sequence has Lan jack MegaMan into an infected microwave, very much like the hacked oven from the FireMan scenario from the first game.
    • A handful of posters around ACDC Town feature images of Battle Network 3 characters, including Tadashii Hikari and Serenade.
    • During the BurnerMan scenario, he and FireMan get into a contest over which is the more Hot-Blooded that gets so out of hand that the entire internet is set ablaze, mirroring the FlameMan scenario from the third game; Lan's even gets the original water-gun program used in the hacked oven from the first game. (It's completely useless, however, and is soon replaced with something better)
    • The Hikari family's doghouse alarm system has usually featured a small local network that you could jack into for goodies; the alarm finally goes off during the events of the game.
  • Cooking Duel: Against Flave Yamakawa.
  • Crossover: with Boktai; Hideo Kojima himself cameos in Castillo late in the story, and MegaMan can meet Django and Otenko in the depths of the internet.
  • Dangerous Device Disposal Debacle: Lan and Mega happen upon a special dark chip left behind by ShadeMan, and learn from Higsby that it's an Artifact of Doom. The game forgets about it during the first tournament, only for it to come up again in the interlude before the second, when ShadeMan decides he wants it back. The boys successfully prevent him from retrieving it, but at the cost of the dark chip permanently infecting Mega Man.
  • Demoted to Extra: After Bass was given increasing levels of importance in the first three games, he is demoted back into being an optional Superboss in this game and keeps that status for the remainder of the series.
  • Difficult, but Awesome: The "Counter" chip series strikes enemies without needing to aim, delivering a Counter Hit from anywhere on the battlefield for instant Full Synchro access. The quirks of Full Synchro also highlight the enemy's attacking frames to help you keep the chain of Counter Hits going, as well, so a folder built around Counter can destroy bosses with ease. The problem is finding the right moment to get the ball rolling, since Counter chips fizzle out when used at any other timing.
  • Early Installment Weirdness: This game, the first to include chip elements beyond Fire, Aqua, Elec, and Wood, is the only one to have Panel-Cracking as an element; Battle Network 5 replaced it with Cursor (and changed SearchSoul's type in the process), while Battle Network 6 only retains Sword, Wind, Cursor, and Breaking.
  • Excuse Plot: The majority of the game follows Lan and MegaMan as they participate in a series of tournaments, meeting quirky characters and helping them solve their own problems along the way. While there are two main sources of conflict in the form of an impending asteroid collision and the shady Nebula organization, the main duo have very little input in either storyline, as they only get involved in the former at the very end of the game; and only actively combat Nebula during short scenarios in between tournaments.
  • Fake Longevity: In theory, the New Game+ system sounds like an excellent way to extend the life of the game without becoming too dull. In practice, it quickly becomes obvious that it was designed to mask the fact that the development team couldn't come up with enough unique single-player content to match its predecessors:
    • The first playthrough only has base-level viruses so, outside of chips grabbed from other sources, the player is stuck with the weakest tier of chips. The second playthrough upgrades the viruses in most areas to their V2 incarnations, while the third and beyond use their V3 incarnations.
    • There are multiple Fetch Quests that have to be done on every single playthrough, such as assembling the C-Slider and the qualifiers for the second tournament.
    • The scenarios for the Double Soul Navis are distributed so that the player obtains all six across three playthroughs. No such care is put into the other tournament battles, meaning that the game might go all three playthroughs without choosing a specific opponent and require more playthroughs to see everything.
    • Blue Mystery Data is already tricky to deal with, but this game adds an extra wrinkle by respawning them with new items for the second and third playthroughs. What happens if you miss one, you might ask? That particular Mystery Data stays on the same "tier" and doesn't update until you pick it up and start a new playthrough. In short, if you miss a Blue Mystery Data relevant to 100% Completion, you get to tack on a fourth and maybe even fifth or sixth playthrough.
  • Fight Woosh: Strangely, the green lines fade-in effect for the tournament matches is the single unique one in the entire series.
  • Game-Breaking Bug: Being the series' worst offender of Obvious Beta, this game has a handful of them. The Virtual Console release fortunately fixed most of these problems:
    • The AquaMan and GutsMan Navi chips and the Park Area explored during WoodMan's scenario cause horrible loading slowdowns when played on emulators or an original model DS. The Park Area version of the issue is particularly onerous, since it can occur when leaving a random encounter or even saving the game. Technically the game has not broken; it "simply" temporarily freezes for as long as 20 minutes and will run normally afterward until you're forced to trigger another slowdown. Thankfully, this was fixed for the DS Lite, patches and AR codes have been developed by fans, and the emulators mGBA and NO$GBA have managed to finally solve the issue.
    • The Free Space battle board. If you link up with the other version before you have all six of the double souls (this means a New Game+ Plus at the very minimum) then your game will crash and corrupt the game's code. And by that we mean that it carries a high chance to permanently break it!
    • When Dr. Regal attempts suicide at the end, there's a dramatic slowdown when Lan and Chaud try to reach out for him. If the player skips the cutscene at this point in the Japanese version, the slowdown will carry over to the credits.
  • Gameplay and Story Segregation: Corrupting MegaMan with Dark Chips to the point he goes evil in the battle interface has no effect whatsoever in the plot.
  • Gold-Colored Superiority: Duo Omega is unique among the powered-up final bosses in that he gets a Palette Swap signifying his status. The primary color is, of course, gold.
  • Guide Dang It!:
    • The Version-Exclusive Content combined with the RNG of the tournament brackets leads to a hiccup: Red Sun completely lacks a scenario to grant access to YumLand's overworld early, and Blue Moon only has one scenario that grants early access to Sharo's overworld. These overworlds are quietly opened up in the endgame, which leads to a problem when the player has to travel to areas they may not know exist.
    • The Meteor Computer has a gimmick where a cutscene will play at random intervals, showing MegaMan being sucked into a black hole and warped back to the entrance, effectively undoing all progress. What the game does not tell the player is that they are supposed to mash the A button whenever the cutscene is triggered, as doing so will enable MegaMan to resist the gravitational pull. If the player fails to realize this mechanic through experimentation or with the help of a guide, the final level can be rendered almost unwinnable.
  • Hand in the Hole: In order to prove that he's a contestant in the last tournament of the story, Lan has to put his hand in the mouth of a stone lion face. It threatened to bite his hand off if he wasn't who he said he was. It's actually a DNA tester.
  • Hero Ball: Lan holds it. He'd win over half of his tournament battles by default if he simply just stayed out of his opponents' lives.
  • Hopeless Boss Fight: It is impossible to win the first encounter with ShadeMan.EXE, as he's immune to all forms of damage and teleports out of the way when hit. The fight eventually ends due to ProtoMan's interruption.
  • Horse of a Different Color: NetFrica (or at least the village Lan goes to) shows that ostriches become the primary transportation with no commentary attached.
  • Inevitable Tournament: This game consists almost entirely of three major tournaments (the closest things the games have to story are treated as B and C plots). The game hits you with a New Game+ that requires you to compete in all three all over again. (If you want to achieve absolutely everything, there are four cycles of the same story for you to pass through).
  • Karma Houdini: Almost every single opponent you fight that commits a crime seems to get off the hook one way or another. Take Ivan Chillski, for example, the self-absorbed prat who hacked government satellites in his own country to cause a blizzard in another (Capcom Science is very, very soft) for the sake of his own personal comfort; now, he gets arrested for this, and even gets a personal interrogation room in Netfrica for it, but is somehow freed and returned to his own country in time to make an appearance for the finale. Or take Paulie, from Netfrica, who nearly caused his village to die of thirst out of childish spite, and yet Lan personally asks for him to be forgiven when punishment looms its head.
  • Let's Meet the Meat: From ElecTown: "It's a sign of a cow recommending you eat beef...But what cow in their right mind would say that?!"
  • Luck-Based Mission: The player can only activate a Double Soul if they manage to draw a chip of the necessary element. The player can't use the Regular Chip system to minimize the luck factor either, as bookmarking a chip makes it ineligible to be sacrificed.
  • Nerf:
    • The max Custom Screen size has been reduced from 10 chips to 8. The 10-chip selection still exists as a perk exclusive to Number Soul, but that comes with the drawbacks and limitations of the Double Soul system.
    • It is impossible to steal any panels from the opponent's back-most column, unlike previous games where combatants can be locked to a single panel.
    • As part of the overhaul to the countering system, the vanilla MegaBuster can no longer be used to counter, unlike in Battle Network 3.
  • Obvious Rule Patch: This game introduces what is commonly known as "Time Freeze Counter": if a "dimming" chip (which stops time and thus is typically easy to use) is activated by one player and the opposite player has their own dimming chip loaded, the opposite player can trigger their chip before the first player's chip fully activates. This mechanic coincides with Invis becoming a dimming chip, effectively creating a check for both. Furthermore, numerous support effects are incompatible with dimming chips.
  • Outside-Context Problem: The main threat looming over the world for the entire game is am asteroid on a crash course with Earth. Said asteroid is artificial and of alien origin, with the program running it designed to wipe out planets it deems to have too much evil.
  • Oxygen Meter: Used during AquaMan's chapter in Blue Moon, when looking for him in the flooded net. This is refilled by stepping into a homepage.
  • Pragmatic Adaptation: The Boktai series' signature gimmick is that the player benefits for exposing the game cartridge to direct sunlight. Since Mega Man Battle Network 4 obviously doesn't have a solar sensor built in, the gimmick is represented by increasing the Gun del Sol chips' HP-sapping effect whenever Lan is jacked in from an outdoors location.
  • Random Events Plot: This game is the straightest example in the series, however, going so far as to have each scenario determined randomly by the tournament system. The game's events are so random, there's no required chronological arrangement (though some official guides behave as though the proper order is the Normal/Heel Navi fight, the Double Soul fight, and then the enemy Boss Battle). In fact, it deserves a Lifetime Achievement Award for this. The events themselves are nonsensical and have no bearing on the plot whatsoever. In the first tournament, you can exorcise a handful of troublemaking ghost Navis, or you can go beat up some roughnecks with a yankee named Tetsu. In the second tournament, you can rescue a Navi that wants to leave the mafia and go straight, or you can have an Iron Chef parody cook-off. In the third tournament, you can travel to NetFrica and participate in a fake village's fake festival worshipping a fake godnote  and then go stop one of the fake gods from killing everybody in the village from drought, or you can go play a few rounds of free kicks in soccer with heavy explosives.
  • Restored My Faith in Humanity: Duo seeks to wipe out mankind because it's wicked (nevermind the fact that destroying an entire planet isn't the most moral thing to do...) but changes after his fight with MegaMan.
  • Remixed Level: Several stages that would be unique in other installments of the series instead take place on Park Area, with just the set of obstacles changing with each scenario.
  • Socialization Bonus: While Double Souls remain Version-Exclusive Content, the Navis that give them can be sent to players with the opposite version of the game. This opens up Free Tournament, which allows the latter player to obtain BattleChips exclusive to that mode and potentially trade them back to the person who gave them the Navi in the first place. For example, only Red Sun has access to Roll Soul and Roll's NaviChips, but only a Blue Moon player with Roll's Navi data has access to the Roll Arrow series, meaning that a Red Sun player who wants Roll Arrow will have to interact with a Blue Moon player.
  • Title Drop: The final tournament is named after the version of the game being played — Red Sun Tournament or Blue Moon Tournament. You can also obtain Giga Chips with similarly identical nomenclature.
  • Took a Level in Badass: You could end up facing Roll in the Electopia tournament (the second tournament). By comparison, in the previous game, she had failed the last round of the N1 Grand Prix preliminaries and didn't even make the tournament proper. She makes use of what's stated to be her previously-existing speed, as well as a newly acquired (during the events of that game, even!) virus-taming and summoning ability. It's also the first time you get to fight her.
  • Trailers Always Spoil: Not that they tried to keep the Big Bad much of a secret, but this trailer still doesn't help things.
  • Traveling at the Speed of Plot:
    • Once you are given access to airplane travel, suddenly traveling to countries around the world is done almost instantly. While it is convenient for gameplay purposes, it causes some logical issues when strict time limit is concerned, most notably during the KendoMan scenario where Lan asked permission to delay their match for what assumed to be a short time period so that he can bring back Mr. Famous who is held hostage in Netfrica. Electopia and Netopia are relatively closer, yet it takes half a day to travel by plane in the second game.
    • The asteroid is ridiculously fast for something that is supposed to be around Pluto in the intro. It only took it around a month tops to reach Earth, meaning it has to be moving at a little less than 3 million meters per second.
  • Undead Counterpart: The highest level of Navis to fight are the SP Navis, which are basically implied to be sort of ghosts of the regular versions, and found in hidden places.
  • The Unfought: It is actually impossible to face the base version of FireMan in Red Sun and NumberMan in Blue Moon, as the games are programmed to always have GutsMan and AquaMan respectively become the player's first Double Soul.
  • Unintentionally Unwinnable: The second phase of ColdMan's scenario requires MegaMan to activate four different satellite dishes by sacrificing four fire chips, each a specific type and with a specific code. Woe unto he who does not have these chips because he fed them to a Chip Trader or traded them to a friend, because unless the Chip Trader decides to give them back, he's stuck. Be especially wary that this doesn't happen on the higher levels, where some of the viruses that drop these chips have disappeared from play.
  • Version-Exclusive Content: The tournament scenarios for Red Sun-exclusive Soul Navis (and thus access to their Soul Unisons) don't happen in Blue Moon, and vice-versa.
  • Video Game Cruelty Punishment: Battle Network 4 treats using Dark Chips on your Navi as the equivalent of giving drugs to your own child, but there is nothing preventing the player from abusing their powerful effects in battle. However, MegaMan loses the ability to use Dark Chips just before the final boss. As a result, if the players had been relying on them for the entire game, they will be forced to tackle the last battle with a crippled HP, no access to Full Synchro or Soul Unisons and no attacks other than the basic buster and chips on the main folder.
  • What Happened to the Mouse?: During the endgame, Dr. Regal explains that two tournaments (named after the game versions) were held to determine who would best be suited to help with the asteroid problem. Lan and MegaMan win one of the tournaments, but the winners of the other tournament is never revealed.

Alternative Title(s): Mega Man Battle Network 4