The term "doujin soft[ware]", also known as "doujin games", refers to a sub-genre of doujinshi — essentially, self-published video games. They can be considered Japan's equivalent to an indie game; while the term "indie" exists in Japan, it is a relatively new concept which refers only to games released through commercial channels.
Doujin games are generally released for Windows-based computers, and, like doujinshi, doujin soft may offer games based on one or more intellectual properties, or entirely original works. The most frequent genres seen in this category of games are platformers, fighting games, RPGs, shoot 'em ups (often Bullet Hell shooters), and visual novels. These games are often released at special Japanese conventions, such as the Comic Market (a.k.a. Comiket) and Reitaisai. Depending on the game's subject matter, they can also be considered fan games (e.g. Grief Syndrome to Puella Magi Madoka Magica) or a homage to another favorite franchise (e.g. RosenkreuzStilette to Mega Man). Most of the time, doujin game developers manage to avoid getting Screwed by the Lawyers concerning the use of another intellectual property, while a few others aren't so lucky, such as Rockmen R: Dr. Wily's Counterattack.
Doujin video games has been around for a very long time. One of the most prominent (and well-known) long-runners of the doujin scene is the Touhou Project series, with its first entry debuting in 1996; since then, it has expanded across 22 official games in the series and a cornucopia of fan-games. That is not to say there aren't other doujin game series that have contended for such a position and legacy. Other doujin series, such as Fate/stay night and the Higurashi: When They Cry series, have even migrated into the realm of mainstream anime and manga.
Obtaining these games, however, can a difficult endeavor for those outside of Japan (freeware ones are easier to get), given the level of obscurity of certain titles and limited print runs. There's also the matter of the games themselves being in Japanese, which can problematic if it's very text-heavy (usually in the case of visual novels and RPGs) or when a game requires you to learn something you can't read. Often at times these games get translated by fans with the knowledge of the Japanese language and the proper know-how of hacking, editing, and re-programming a game to run in a completely different language, and the willingness to do so. Also, some games are already in English and comes with English documentation, which makes playing them easier.
In recent years, there have also been a very small but growing number of publishers, independent or otherwise, that localize these games outside of Japan and bring them overseas. There are also a few specialty online retailers that can import the original pressings of a doujin game, if copies are available in stock and if shipping the game in question isn't taxing on your wallet. Additionally, some doujin games have been re-released and localized digitally through digital distribution services such as DLsite, and Steam to make things easier for those who could not attend to the events where they were originally released in and alleviate the cost of importing the games overseas. Some games even get some quality-of-life improvements or even special bonuses one way or another for their overseas release, depending on the publisher.
Notable doujin soft titles include:
- A Witch and Fabricated Shadows
First-Person Shooter
- Another Bound and Another Bound NEO (a Metroid Prime-esque freeware game)
Run-and-Gun
- Armored Hunter Gunhound (a mecha run-and-gun game)
- Gigantic Army
- Gun Star (a run-and-gun Lucky Star fan-game; not to be confused with Gunstar Heroes)
Third-Person Shooter
- Dysnomia
- Homura Combat and its expansion pack (a Puella Magi Madoka Magica meets Earth Defense Force fan-game)
- Soul Saber 2
- The Legend of Derella (A The Legend of Zelda-styled game featuring characters from Idol Master)
Metroidvania
- Bunny Must Die (from the creator of the Gundemonium series)
- Fox Eye
- Holdover (a Metroid-inspired, timing-based Platform Game with an emphasis on maintaining an Oxygen Meter)
- Sacrifice Girl (an Under the Sea Metroidvania with Survival Horror elements)
- BLUE GUARDIAN: Margaret (a highly Ecchi Metroidvania Platform Game with more Metroid-inspired gameplay compared to the above two.)
- Ghost 9
- Ghost 92
- HACK 9
- HACKER 9
- HACK 9 Solid
- Blood Over
- Cinderella Escape!! 2 Revenge
- Cröixleur
- Crescent Pale Mist (also a platforming game)
- Duo Princess (a Threads of Fate fan-game by EasyGameStation, the creators of Recettear and Chantelise)
- ElePaper Action (a Read or Die fangame also by EasyGameStation)
- EXTRAPOWER: Giant Fist
- Fairy Bloom
- Grief Syndrome (a Puella Magi Madoka Magica beat 'em up by Twilight Frontier, the creators of Mega Mari)
- Mitsurugi Kamui Hikae (also a hack-and-slash game)
- Ore no Yome Offline (a Dungeon Fighter Online-esque beat 'em up staring various characters of anime and light novel series)
- Princess' Edge - Dragonstone
- No Net Card
- Acceleration of SUGURI and its expansion pack
- Acceleration of SUGURI 2
- Akatsuki Blitzkampf and its expansion pack
- EN-Eins Perfektewelt and its upcoming expansion pack
- Arm Joe
- Azumanga Fighter
- The Black Heart: A fan-game using the M.U.G.E.N engine, created by Andrés Borghi.
- Blue Mischief
- Crimson Alive
- Angel Star Road (Crimson Alive's spiritual successor)
- Big Bang Beat and its sequel, Big Bang Beat Revolve
- Elemental Battle Academy (from the same creators of Magical Battle Arena; uses third-person combat and gunplay)
- Magical Battle Festa (Elemental Battle Academy's spiritual successor)
- Eternal Fighter Zero series
- Fate/sword dance (a fighting fan-game of Fate/stay night)
- Furry Friends Fight! (a fighting fan-game of Kemono Friends)
- Fuuka Taisen (a fan-game of Mai-HiME and Mai-Otome)
- Magical Battle Arena (an aerial combat crossover fighting game featuring characters from various and popular magical-girl anime series)
- Touhou Sky Arena (Magical Battle Arena's spiritual successor featuring various Touhou Project characters)
- Magical Battle Arena NEXT (a sequel to and crossover between both of the above games)
- Maribato!
- Mega Man X: Rush to Battle (a Mega Man X fighting game)
- Melty Blood and its expansion packs
- Million Knights Vermillion
- Monster
- The Queen of Heart
- Soul Saber
- Tenshou Tenshi VALFORCE (a Virtual-ON doujin game with mecha-musumes)
- Terrordrome the Game: Rise of the Boogeymen (A fighting game starring various horror movie characters)
- Touhou Project (the spin-off fighting games Immaterial And Missing Power, Scarlet Weather Rhapsody, Hisoutensoku, Hopeless Masquerade, Urban Legend in Limbo and Antimony of Common Flowers)
- Umineko: Golden Fantasia (a fighting Umineko: When They Cry gaiden game)
- Under Night In-Birth and its expansion packs
- Vanguard Princess
- Windom XP:
- Bootfighter Windom XP SP-2 (only the game in the series that is free)
- Ultimate Knight Windom XP and its expansion pack
- Ultimate Knight Windom SV
- Yatagarasu (an indie game from former SNK developers)
- Eryi's Action (a Super Mario Bros.-esque platform hell game)
- Koumajou Densetsu (a Castlevania homage using Touhou characters)
- Lethal Crisis and Lethal Crisis ProtoSphere (a spin-off series of Lethal Application; the latter is also a rogue-like)
- Ragna Chronicle (a Ragnarok Battle Online-eqsue Mega Man game)
- Rockmen R: Dr. Wily's Counterattack (a fan-sequel to Rockman 9)
- RosenkreuzStilette (an homage to the classic Mega Man series as well as various manga, anime, and visual novel series)
- SorcerLand (a retro-styled action-platformer featuring anthromorphic characters)
- Tobari and the Night of the Curious Moon (a Super Marios Bros.-esque platformer with gameplay elements from the Kirby series)
- Cinderella Escape!
- 99 Spirits (also a puzzle game)
- Arcanum Knights
- Chantelise ~A Tale of Two Sisters~
- EXTRAPOWER: Attack of Darkforce
- Fortune Summoners
- Grana Embrace (Strategy RPG; from the doujin circle behind Crescent Pale Mist)
- Fairy Bloom Freesia
- Ragnarok Battle Offline (a fan-game of Ragnarok Battle Online)
- Kemono Friends Cellien May Cry (a roguelike dungeon-crawling Kemono Friends fangame by Ryu Sakamoto; also a stylish action game)
- Sword Of Rapier
- Recettear ~An Item Shop's Tale~ ("Capitalism, ho!")
- World of TWAIN (an Eastern RPG set in the TWAIN / TWIN universe)
- Akashicverse ~Malicious Wake~ (a surreal shoot 'em up where special weapons are activated akin a fighting game)
- Aurora Blast and its sequel (a shoot 'em up series with very fast bullet patterns)
- Blue Wish
- Blue Wish Resurrection and Blue Wish Resurrection Plus
- Blue Sabers
- The Chaste Full-metal Maiden -Leiria- and its remake (formally retail doujin games now officially freeware)
- Cho Ren Sha 68k (a freeware retro-styled shooter)
- Crimzon Clover
- Graze Counter
- Green Wind
- Eden's Edge
- Eden's Aegis
- eXceed series:
- eXceed-Gun Bullet Children-
- eXceed2nd-VAMPIRE- and eXceed2nd-VAMPIRE REX-
- eXceed3rd-JADE PENETRATE- and eXceed3rd-JADE PENETRATE- BLACK PACKAGE
- Vertical shooters by Orange_Juice:
- Flying Red Barrel ~Diary of a Little Aviator~
- QP Shooting series
- Hitogata Happa from the Gundemonium series
- HECTOR '39 (a freeware shoot 'em up featuring Miku Hatsune)
- HELLSINKER
- The Hurricane of the Varstray -Collateral Hazard- (from the doujin circle behind Trouble Witches)
- Lethal Application
- Meglilo The Witchborg
- Patriot Dark (a formally retail DoDoPatchi-esque freeware shooter)
- Rozen Diadem (freeware shooter based on Rozen Maiden)
- RefRain ~prism memories~ (from the makers Samidare and Seihou)
- ring^-10 (a retro-styled shooter; from the makers of Patriot Dark)
- Samidare
- Seihou
- Shuusou Gyoku
- Kioh Gyoku
- Banshiryuu
- Strike Witches STG (a freeware PC one, not the Japan-only Xbox 360 one)
- The Tale of ALLTYNEX series:
- Touhou Project, to this day the undisputed king of doujin videogames in general, thanks to its combination of Cute 'em Up with Japanese mythology, massive amounts of fanart and lots of characters with plenty of room to adapt to whatever a doujin work needs.
- TWINS / TWAIN series:
- Twilight Insanity
- Twilight Refrain
- Alternative Sphere
- Stella Vanity
- Warning Forever
- Wolflame
- Zillion Beatz (a music-based vertical shooter)
Horizontally-scrolling Shooter
- Armed Seven
- cloudphobia
- Diadra Empty
- EXTRAPOWER: Star Resistance
- Gundemonium, GundeadliGne, and Gundemonium Recollection from the Gundemonium series
- PriZhm
- Revolgear II (freeware Gradius-esque shoot 'em up)
- Revolver360 and Revolver360 RE:ACTOR
- Rolling Gunner
- Satazius
- Horizontal shooters by Orange_Juice:
- Supercharged Robot VULKAISER
- Trouble Witches series:
- Trouble Witches Episode 1 ~Daughters of Amalgam~
- Trouble Witches Episode 2 ~With Descendents of Ancient Dragon the Souless~
- Zangeki Warp
Rail-Shooter
- Gunner's Heart
- SHAFTDIVER
Other
- Ether Vapor (a shoot 'em up with changing gameplay, going from a vertical shooter, horizontal shooter, and even a rail shooter)
- Astebreed (spiritual successor to Ether Vapor)
- Erst Kerf (an RPG adventure game with an overhead shoot 'em up perspective)
- Every Extend
- QUALIA (localized as Qlione by Rockin' Android)
- Daitoshokan no hitsujikai: Houkago Shippo Days
- Fate/stay night
- Higurashi: When They Cry
- Rose Guns Days
- Umineko: When They Cry
- Trif
- Tsukihime
- Valhellio (also a vertical shoot 'em up)
- 100% Orange Juice!, a crossover game by Orange_Juice featuring characters from some of their games (SUGURI, Flying Red Barrel, and QP Shooting)