Bikou considers Vali as his partner while Vali respects Bikou as his friend and subordinate. The two are commonly seen together along with Arthur.
Bikou finds Issei interesting. He watches Issei's strange development with interest and finds it funny.
Rias is on bad terms with Bikou mainly due to Bikou inventing her "Switch Princess" nickname and constantly makes fun of her.
Bikou shows little to no respect for Sun Wukong despite the fact that he is Bikou's ancestor. Bikou, however, is afraid of Sun Wukong's strength and wishes to avoid him if possible.