Yu Xiang

Talent: Omnireceptacle; Black Death of Harmony

Kou is a wandering warrior with unparalleled martial arts talent and the leader of the Sinners, a group of wandering criminals. He is an enemy of the Forest of the Greats, but he is a mysterious figure who knows the origins of the Forest of the Greats.

Best friend of Seiya and one of Forest of the Greats' founders. While Seiya was pursuing world peace, Kouu wanted to make a place for Returners to coexist. However, eventually their ideals clashed and Kouu ended up killing Seiya.

He spent his last moments embracing Charlotte at the graveyard of his comrades before finally passing on by way of her Talent.
(Source: Reincarnation no Kaben Wiki)