Sae struggles to fit in at a prestigious private girls' high school full of refined young ladies. Every lunch break she plays mahjong alone on a phone app, keeping it secret because she suspects the hobby is out of fashion. One day Chisei, the most popular and charismatic girl in her class, finds out. The two have opposite personalities and would normally have nothing in common, but mahjong turns them into playmates. The show is a light comedy about school life, built around this unlikely pairing.