Abandoned as a child by his mother, Hasumi Sachiyo, Fujishima Haru 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 Sakurai Kyoko and Tashiro Miki, 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 Toya Erina who not only is their teacher but also their friend. One day, Erina is approached by her old friend Kobayashi Rumiko about a candidate in the research she is conducting with professor Tatabe Shinichiro and Tokunaga Atsushi 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,

大人になっても幼児の知能しかない主人公。彼は生まれながらの知的障害者で、その人生は嘲笑に満ちていた。しかし人のいい彼は少しもくじけず、陽気に生きてきた。そんなある日彼に、大学の偉い先生が頭を良くしてくれるという夢のような話しが舞い込んだ。