Sekisei Inko  

セキセイインコ

Kaneda, a young man, experiences trauma-induced amnesia following the discovery of his classmate and friend's corpse. After receiving medical attention at a hospital, he is picked up by an enigmatic benefactor before resuming school. Despite his attempts to reconstruct his recollections of the incident, Kaneda's memories have taken on a fantastical form - that of a moon-shaped head creature. Along with this otherworldly being, they embark on a quest to unravel the mystery surrounding Hiwako's murder.