Nisekoi Doumei.

Synopsis

When classmates Mayuri Asana and Youji Aikawa catch their lovers kissing each other, they form a secret pact: to get back at them, Mayuri suggests that she and Aikawa have a love affair of their own. But these sorts of clandestine dealings are never simple, and what started out as a business-like conspiracy soon sparks something between them. Initially a romance born from revenge, they must now deal with the troubles and secrecy that come with being partners in crime and love. (Source: MyAnimeList)