Yakumo Fujii

The primary male character he became Pais Wu and companion when a rampaging Takuhi Pais demon friend fatally wounded him. Before he could die Pai merged his soul with her own transforming him into a Wu which in turn made him immortal as long as Pai lives. His father had previously found Pai and promised to help her become human so Yakumo tries to keep that promise. Source: Wikipedia