Futago Kissa to Akuma no Ryourisho

Kagari has been in love with Hazuki since he was young. However, he has been unable to confess even now and is currently working part-time with her and her twin sister Mizuki at a coffee shop. One day, a dumb fairy named Kiki comes out of a book and tells Kagari she'll grant his wish and forcibly ties his love line with Mizuki instead of Hazuki.

(Source: Amazon, translated)