KoiKoi is a Japanese hanafuda card-matching game. The goal is to obtain special sets of cards (or yaku) by drawing and discarding from a hand of 8 initial cards. Upon obtaining a yaku, the player must choose to end the game with their current hand, or declare koi-koi to continue for more points. The player with the highest-scoring yaku wins.
Note that this version of the game is played in Japanese only. However, it can be used on any region device without the need for additional language software (like CJKOS).