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Kurumi is an android who isn't very bright. Her guardian Chiaki is a bit of a lunatic, and the two of them go through high school alongside Sakina and Shiyuki. Sakina is cool and composed until something sets her off laughing, which doesn't take much. Shiyuki is the only sane one(?), and the question mark is doing a lot of work there.

Their days are mostly nothing in particular. They upgrade Kurumi, fuss over her like a pet, and chat about whatever comes up.

(Source: MAL News)