Danjo-hi 1: 39 No heikō sekai de sumire no sakurasō (sakura sou) wa futsūjanai...

A parallel world with a 1:39 male to female ratio. Sumire, the older sister, notices something strange about her younger brother, Sou. Sumire challenges her brother's "unusual" affection and the truth of love and longing in this world.

This is a fan comic of the manga "A Parallel World with a 1:39 Male to Female Ratio is Surprisingly Normal."