Room 309, also known as the Sweet Room (スイートルーム, Suītorūmu), is one of dorm rooms in Setouchi Keijo Training School.

It's rumored that this room is designated for those who barely passed the exam. Many students have lost their confidence and dropped out. It's also the closest room to the emergency exit. By the time Sayaka Miyata and Nozomi Kaminashi joined to the room, there are only two remaining residents, Kazane Aoba and Non Toyoguchi. Following the class exchange event, all of the residents have been promoted into the Elite Class.