Takuma Sakamoto is formidable inside the game Cross Reverie and awkward with people outside it. Summoned into another world as his Demon Lord avatar Diablo, he meets Shera and Rem, who each claim to have called him there. Their attempt to bind him magically rebounds, leaving the two summoners wearing enslavement collars instead.
Diablo responds to unfamiliar conversations by performing the arrogant character he played in the game. That makes overwhelming combat power an imperfect solution: he can terrify an opponent more easily than explain himself to the people travelling with him. The adventure repeatedly sets the role he is acting against the socially anxious person inside it.
Shera and Rem’s closeness to Diablo does not make the collars a solved problem. The group searches for a way to remove them, even visiting a slave market for information. Their uneasy arrangement gives the travelling party a practical shared concern alongside its sexual comedy and battles, rather than turning a reflected spell into uncomplicated companionship.