Higashino Keigo

Someone is trying to kill Maejima, the unassuming Archery club adviser and Math teacher at Seika Women's High School. What appears to be pure, dumb luck has gotten him through several attempts unscathed, but he has no clue as to the perpetrator and the Principal would rather not involve the police in what's "surely just a student acting out". With the entire faculty and student body as his suspects, Maejima struggles to discover the culprit before his luck runs out.

The main protagonist, the shy Jun Naruse, is a rather average guy who works for a electronic company and loves to draw. He falls in love with Megumi whom he met at a shop selling drawing materials and an intimate relationship develops. One year later the office 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?