Taiko no Tatsujin: The Drum Master!

A good way to grind coins is to change your date and time on PC then play the bonus songs. Rinse and repeat until you have enough coins for desired items. If you're on Xbox One simply play the daily songs. A tip for Xbox: Some songs on extreme are pretty easy. Homura on extreme is pretty easy after some practice. The song will award 90 coins if you get a full combo!