In order to cheer Haruto up after his anime was such a flop, Itsuki gets him as well as Nayuta, Miyako and Chihiro together so they can play a TRPG. Itsuki usually plays girls in games, but for some reason, Chihiro makes out their character to be Itsuki’s character’s little sister, which leads to Nayuta and Miyako also making their characters sisters of the other two. Haruto becomes the GM and does whatever he wants.
Onee-sama and I were just doing 
obscene things together in public!
Ich und meine Onee-sama haben uns nur in der
Öffentlichkeit unzüchtigen Handlungen hingegeben!
¡Mi hermana y yo solo hacíamos
cosas pervertidas en público!
¡Mi hermana y yo solo hacíamos
cochinadas en público!
Il y a méprise !
Io e la sorellona ci stavamo solo lasciando andare
alle nostre voglie perverse in pubblico!
A Onee-sama e eu estávamos apenas
fazendo coisas indecentes em público!
Мы с сестрицей всего лишь публично
предавались любовным утехам!