The responsible eldest son, Hideki, and the spoiled second son, Kenji. Both were born from Eiko's easy-delivery hips, but their personalities differed. Without regard for others' presence, Kenji would cuddle up to Eiko's buttocks, while Hideki suppressed his own desire to be pampered as the eldest... One day, Kenji accidentally catches Eiko performing dildo masturbation as part of her daily routine to maintain her easy-delivery hips. Seeing his mother's massive buttocks firsthand, Kenji's love for butts explodes, and he advances towards Eiko's buttocks...
