No it isn't, this is an original story. Beside i don't know where you get that from but really few manga are based on games. Often manga are made to look like a game, but they aren't based on a game. And the rare few that are based on game often aren't anything like the game.
Also, half the time that games are related to manga, the games Is based off the manga rather than the other way round.
This^, i feel, was the more important reaction. Games are made from manga indeed.
Is this a game? Anyone knows? Normally, author make games into mangas.. I wanna play it.