"Can't cum yet?" The simple-minded stepsister whispers lewdly as she rides him in a piston-like position, repeatedly ejaculating without him ejaculating! (ROYD-274)

Two people who suddenly become 'siblings' due to remarriage. The taciturn and enigmatic stepsister, Hikari. Initially awkward and quiet, their relationship changes one day due to an unintentional 'whisper'. The sister's lewd whispers in his ear. The younger brother, unable to resist the sudden temptation. Unable to withstand the sister's seductive whispers, the younger brother's rationality crumbles. He gradually becomes obsessed with his sister because of her intimate and lewd words.