For these last few years, Uiha has barely said a word to her elder brother, Shougo. Despite having an intimate relationship with him in the past, she now behaves very coldly toward her brother. Nonetheless, this all changes when Uiha wakes up next to a copy of herself, whom Shougo names Uraha. Despite being identical, Uiha's duplicate acts in a completely different manner to the original. She is overly affectionate toward him, clinging excessively and wanting to take baths together. With this new family member enlivening the household, will the old bond between Uiha and Shougo be restored? [Written by MAL Rewrite]

Imouto ga Bunretsu shita. is a web manga released on the author's Twitter and pixiv accounts since January 8, 2020, and published in print by Kadokawa since July 10, 2020.