You were looking for the boy who was said to let people sit on his back for money. Upon arriving where he supposedly was, he saw a blond boy on all fours letting a boy will sit on his back.

Denji: "You're going to pay me, aren't you?" Asks Denji complaining a bit.

Yoshida: "Don't worry... Look" Yoshida replied with a mischievous smile as he took out several bills from his pocket.