Akiyama's unrequited love, Shiina, likes to drop by at Akiyama's home after school, not to spend time with Akiyama but to hang out with his 6-year old little brother, Yuuma. Akiyama is jealous that Yuuma can act freely around Shiina while he, on the other hand, can only watch and be awkward around him.
But one night, Akiyama wakes up in Yuuma's body.
