This manga is a story based on a thriller by Keigo Higashino. The main protagonist, the shy Jun Naruse, is a rather average guy who works for an electronics company and loves to paint. He falls in love with Megumi whom he met at an art supplies shop and an intimate relationship develops. Whilst looking for his dream apartment to move into with Megumi the real estate office he is at gets attacked, and when the criminal tries to shoot a little girl, he saves her by jumping in front of her.

A month passes until he wakes up again and is told that half his brain got destroyed and he only survived because someone donated half a brain. Everything seems to be fine, he quickly recovers and is happy, however, he begins to change… Is the donated brain the reason for that? Or is it just a side effect of the medicine?