Yonshimai wa Otouto to Harem Shitai!

A young man finds himself living with his four older sisters, who have decided to take their relationship with him to a new level. The sisters, each with their own distinct personality, are determined to create a harem-like situation with their younger brother, blurring the lines between familial affection and romantic desire.

As the brother navigates this unexpected dynamic, he must deal with the advances of each sister while trying to understand their true intentions. The sisters compete for his attention, leading to intimate and awkward situations that challenge the boundaries of their sibling bond.