Itoshiki Enishi is the older brother of Nozomu Itoshiki. He is the first child of the Itoshiki family.
His name in kanji, written sideways with the two kanji for itoshiki squeezed together, resembles Zetsuen, which means "disinherited", alluding to the fact that for most of the series, he remains unseen. Even his face remains a mystery until late in the manga.
He supposedly worked as a divorce attorney but currently works as a posthumous marriage counselor, giving marriages to people that could not get married while alive to help them cut their ties to the world.
He is also revealed to be the "shadow doppelganger" that Tokita brings in to substitute for Nozomu.