A young woman wakes up and finds herself in a space between dimensions. She is confronted by a young boy who tells her that he attempted to move from his world to hers. However, he made a mistake and ended up colliding into her mind. In doing so, he accidentally wiped out all of her memories. Eventually, the boy, Orion, will become further ingrained in your mind the longer he stays in your mind, and eventually you'll end up losing all sense of self. But all is not lost. There is one way to get him out: Regain your memories.

At this point, she is offered a choice between four worlds: heart, spade, clover, and diamond.

An interesting spin on the otome genre, ''Amnesia'' is an [[{{RomanceGame}} Otome Game]] released by Otomate in 2011, who quickly became very popular thanks to its innovative story: instead of having the heroine attempt to win the heart of a guy, the heroine is in a pre-existing relationship. A part of the gameplay is to help the heroine adjust to the now-unfamilar world without arousing the suspicion of those close to her. It also spawned three fandiscs, ''Amnesia LATER'' and ''Amnesia CROWD'' for the PSP and ''Amnesia WORLD'' for the PSVita (the original game got a port for the PS Vita called ''Amnesia V Edition'' as well), a manga adaptation and an anime by Creator/BrainsBase that aired in the Winter 2013 season.
!!Amnesia contains examples of:

* ArtShift: The artist changed her style between ''LATER'' and ''CROWD'', the sprites remain the same but the CG's style is definitely different.
* BeachEpisode: Okay, it's a pool, but it still counts.
* BeCarefulWhatYouWishFor: Ikki. [[spoiler:As a child, he wished to be popular. As a result, any woman who looks him in the eye falls in love with him.]]
** [[spoiler: Ukyo made a wish to (Orion's superior) Neil to save the Heroine's from death and for him to be able to be with her again at the cost of her not remembering him. The problem is that even if he [[IWantMyBelovedToBeHappy lets her be happy with another man]], the wish cannot be fulfilled and Ukyo remembers every world the Heroine dies by his hand or fell in love with another man and dies in her place because their existence in the same timeline is an anomaly.]]
* CastFullOfPrettyBoys: Well, it is an otome game.
* ChildhoodFriendRomance: Heroine with Shin or Toma.
* ClearMyName: A good part of Shin's route. He's considered a suspect in the heroine's accident because his father accidentally killed someone. [[spoiler:In reality, Toma was responsible for injuring the heroine a second time.]]
* ColorCodedCharacters: The heroine is pink, Shin is red, Ikki is blue, Kent is green, Toma is yellow and Ukyo is purple. As for the supporting characters, Orion is grey, Sawa is light green, Mine is light purple, Waka is brown and Rika is hot pink.
* [[spoiler:DeadAllAlong: The heroine, at least in Joker world. She gets better by virtue of a time rewind.]]
* DemotedToExtra: In the anime, Kent only got a single episode focusing on his route, while the rest of the guys got at least two.
* ExtremeDoormat: The Heroine, post amnesia. Especially jarring in episode 9 when she hesitates to leave [[spoiler:Toma even though Orion just told her that Toma has been ''drugging her for days.'']]
* FanserviceWithASmile: The heroine (and most of the cast) work at a [[CosplayCafe maid and butler cafe]].
* FourTemperamentEnsemble: Shin (choleric/melancholic), Toma (sanguine/choleric), Ikki (phlegmatic/sanguine), Kent (melancholic/phlegmatic). Ukyo is an odd case of being (leukine). By default he's (melancholic/phlegmatic), [[spoiler: but his darker split personality is (sanguine/choleric).]]
* [[spoiler:GroundhogPeggySue: Ukyo. This is done by Neil as he needed Ukyo's wish to come true to gain back his powers after the conditions were fulfilled.]]
* HandsOnApproach: One of Ikki's CG.
* HiddenEyes: Ikki's fangirls, with the exception of Rika [[spoiler: and the heroine.]]
* IdentityAmnesia: One of the heroine's problems. She usually finds out ''who'' she is very quickly, though. The problem is she doesn't remember anyone else.
* InstantFanClub: Ikki has one and they are ''awful''. There's at least one ending where their antics result in the heroine dying. Interestingly, [[spoiler:the heroine herself is actually a member in some routes. It's why she's dating Ikki in his route]].
* InvisibleParents: The heroine's parents in most of the routes except Ikki's, due to the heroine living alone.
* JekyllAndHyde: [[spoiler:Ukyo, as a side effect of going through so many worlds where either he or the heroine died.]]
* MultipleEndings
* ObliviousToLove: [[spoiler:Toma, despite being very observant about other things. He doesn't pick up on the heroine's pre-amnesia hints that the guy she likes is him. It's part of what drives his yandere phase.]]
* OnlyOneName: Everyone calls each other by their first names.
* StarCrossedLovers: [[spoiler: Ukyo and the Heroine at a cosmic definition. One of them has to die as neither of them are suppose to exist together after the Heroine is fated to die from the injuries she sustained in her university's fire. Luckily, Ukyo's wish to Neil was granted when the Heroine survived after her fated death day in their original world and [[EarnYourHappyEnding was able to be with Ukyo.]]]]
* UmbrellaOfTogetherness: Kent and the heroine when it rains at the festival.
* VictoriousChildhoodFriend: Toma and Shin in their respective routes.
** UnluckyChildhoodFriend: Toma in Shin's route and presumably Shin in Toma's route.
* {{Yandere}}: [[spoiler:Toma]], especially after he brings out the cage.
** Ikki's fangirls definitely count.
* YouGottaHaveBlueHair: Ukyo has green hair. Ikki has blu[[HairColorDissonance ish]] silver colored hair.
** One of Ikki's faceless fangirls has blue hair.