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.
You're basically guaranteed fanservice 
scenes, gore, and horror in that world.
Viel nackte Haut, Groteskes und
Horror gehören da dazu.
Básicamente, las escenas gore
y de terror están garantizadas ahí.
Básicamente, las escenas gore
y de terror están garantizadas ahí.
Les scènes érotiques y vont de pair
avec le gore et l’horreur.
In quel tipo di ambientazioni, fan service,
scene sanguinolente e horror sono la regola.
No universo deles, é basicamente garantido
cenas de fanservice, violência e horror.
Там жуть, жесть и эротика
всегда идут в одной связке.