Abandoned as a child by his mother, Sachiyo Hasumi, Haru Fujishima is a mentally challenged man that has grown up and worked at the Sakurai Bakery as a baker. Working with him at the bakery is the owner Kyoko Sakurai and Miki Tashiro, a girl who is also mentally challenged and is like a sister to Haru. At night, after the bakery is closed, Haru and Miki attend a night class with other mentally challenged adults. Their teacher at the class is Erina Toya, who not only is their teacher but also their friend. One day, Erina is approached by her old friend Rumiko Kobayashi about a candidate in the research she is conducting with Professor Shinichiro Tatabe and Atsushi Tokunaga that could possibly increase the intelligence of the mentally challenged. Reluctant at first, Erina changes her mind when she sees the resolve in Haru to become smarter so that his mother will come back for him. With the success of the surgery, Haru becomes more and more intelligent. However, with his newfound mental...