Marshmallow, Imouto, Succubus

Storyline & Plot Overview

The narrative follows a young man whose daily routine revolves around his characteristically adorable younger sister, known throughout their family circle for her gentle personality and soft, marshmallow-like presence. However, the domestic status quo undergoes a sudden, absolute transformation one ordinary day when she unexpectedly experiences a profound supernatural awakening, transitioning into an elite Succubus entity.

This mystical metamorphosis instantly triggers an unyielding, biological surge of proactive charm and magnetic attraction, focusing her newly discovered instincts almost entirely on her unsuspecting older brother.

The core story focuses heavily on the younger sister’s relentless, calculated “charm offensives” and the protagonist’s profound flustered state right inside their daily shared environment. Faced with a constant wave of high-stamina, uninhibited enthusiasm behind closed doors, the older brother is forced into a highly challenging game of mental composure and psychological endurance. He must continuously navigate her powerful, proactive presence while desperately trying to maintain standard boundaries within their everyday household routine.