Urara-chan no Naka no Hito

Overview

Urara would really like to be a normal high school girl, but her mad scientist older sister and mother make this a difficult goal. For their latest experiment, they've fused Urara's neighbor and childhood friend Takaharu into Urara's body. After discovering this, Urara destroyed some of the experimental apparatus in a fit of rage, leaving them stuck with each other for the time being. Takaharu is a high school graduate who sells erotic manga while waiting to retake his college entrance exams. Takaharu takes over Urara's body when she falls asleep or passes out, and, to Urara's embarrassment, has been using it as source material for his manga. Will the two of them be able to deal with sharing a body until Urara's family can put things right? (Source: MangaHelpers)

Source: AniList