Урушібара Лука

Second year in Kasensou Private Prepatory Academy. Mayuri's classmate. Luka has the personality of a polite, well-groomed, and justified kind of person. Uses honorifics specifically with Rintarou. Luka doesn't push their opinions much upon others, but when they do they become quite bashful and blush quite a bit. Because they're quite serious by nature, they simply believe what others say. Thanks to that, Luka thinks all the ridiculous stuff Rintarou talks about is real. Rintarou makes them out to be his student on their own, and is currently in the middle of brainwashing them. A very shy person, Luka often turns down Mayuri's requests to cosplay.

In Episode 8, Luka succeeded in changing their sex to female by sending a message to their mother's pager, telling them to consume more vegetables to alter their sex. In exchange of dating Rintarou, Luka undid their message which turned back their sex to male again.