Wagaya ni Majo ga Yattekita!

Black witch Kiri is defeated in a magic war and expelled to human world. She can not use magic there unless establishes a contract with a human being - and that human happens to be our protagonist. Kiri only desires to return to her primary world and conduct revenge at first, but her heart gradually softens. However, two white witches are soon sent to the human world to kill Kiri...

[From vndbreview]