Released via Vol.6 of the book-type iteration of DiscStation98, Imohori is essentially a digital adaptation of the Page One variant of the card game Millionaire/Trump, and was derived directly from a programming exercise assigned to rookie hires. Neither the game itself nor any of the extremely original player-characters have anything to do with Madou, but because they slapped a bunch of Madou characters on the playing cards, the game's trapped in Madou-Puyo IP limbo and hasn't been reissued outside of Madou-specific initiatives.
There's not much to it, not does it offer any real narrative or character content beyond basic win quotes, but there's a rule variant that makes the Draco card OP, so ya gotta respect it.