Kōichirō Endō is a supporting character in the series, first introduced as a classmate of the protagonist, Tasuke Shichiri. He is a Japanese student with dark blonde hair and petrol-colored eyes. Alongside his fellow classmate Takashi Nomura, Endō is one of the few humans who becomes aware that Shaorin and the other spirits are supernatural beings. His primary motivation in the story stems from his romantic feelings for Ruuan, the cheerful spirit of happiness. Endō's role is that of a background school friend, often appearing in scenes at school or during group activities, and he participates in the lighthearted misunderstandings and comedic situations that arise from the spirits' presence. His relationship with Takashi is that of a close friend who shares similar bewilderment at the extraordinary events around them. Endō does not possess any special abilities and shows little character development beyond his persistent crush on Ruuan, serving as a typical teenage boy caught up in the fantastical happenings caused by the guardians.