Harem Royale - When The Game Ends -

Harem Royale ~ When The Game Ends ~ (恋愛ハーレムゲーム終了のお知らせがくる頃に Ren'ai Harem Game Shuuryou no Oshirase ga kuru Koro ni) is a Japanese horror harem manga written by Ryukishi07 and adapted to a manga by Yukari Higa.

Plot
Minamatai Asunaro is walking home from school one day when he discovers a mysterious bottle. Once he opens it, he sets free the demon Zepafur who wishes to repay the debt. To do so, she decides to make his harem dreams come true in the Lovey Dovey Harem Royale!

Unknown to Minamatai, if girls in the game fail to win over his heart, they will die and face eternal damnation in hell.

Volumes
There are 4 current volumes of Harem Royale ~ When The Game Ends ~, though only one has been translated into English.