Kusakabe Yuki overhears some girls saying mean things about her. Gossip is not an uncommon problem among high school girls, but Yuki is particularly worried that it's happening because she's a demi. Tetsuo is sympathetic to thr concern and makes up his mind that, as her teacher, he must protect her. Hikari, a fellow demi, feels the same way.
The story takes place in an age where "Ajin" (demi-human), more casually known as "Demi," have slowly started to become accepted into human society. Tetsuo Takahashi is a biology teacher who ends up teaching three such Demi, hoping to understand more about them while also managing to catch their attention.
