MeRAMAN, the guy behind the Tetris Grand Master port, (who eventually had to discontinue development and distribution due to the Tetris Licenser sendiing him a rather nasty warning) has released a Hanafuda game where you play Koi-Koi style against the CPU. In Koi-Koi style the player throws a card on the same suit card to capture them. The winner is the one who makes the special combination of several cards which is called a "Yaku".
Like Tetris Grand Master, NDS Koi Koi has a wifi ranking table built into it. While the quailty may not stand out from the screenshots alone, what you are getting here for free feels solid. There's some good presentation with nice BGM and sound effects throughout. With all of that combined, this game stands out from the average homebrew card game and gets my recommendation!
There are many guides online for hanafuda, even if you are unfamiliar with it i don't think it will take much time to get used to. Summer Wars was awesome btw