俺の妹が最高のオカズだった　クールな彼女がＨのときだけデレる理由

Say, Onii-chan—you’re really a hopeless siscon, huh.

After being seen busting one out on eroge about younger sister by his actual younger sister, for some reason, she is taking care of it with her mouth. Despite being scorned for having dispositions of lusting for his own biological younger sister, the play is becoming extreme; from titty f*ck, to loli cosplay blowjob, and even unprotected creampie! Is this younger sister really going to cure her older brother sexual disposition!?