Heads

Heads (ヘッズ) is a manga series by Keigo Higashino with illustrations by Motoro Mase. It was serialized in Young Sunday.

Plot
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. A few days later, the office gets attacked, and when the criminal tries to shoot a little girl, Jun saves her by jumping in front of her.

A month passes until he wakes up again and is told that half his brain was 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 this change? Or, is it just a side effect of the medicine?