Saredo, Futari wa Kusare Koi

I've known this guy since elementary school.

Childhood friend? No. He's my arch-nemesis!

Muku Mochigi, a high school student, has a childhood friend, Kyou Yakumo, with whom she's had a conflicting relationship for the past 10 years. The two are complete opposites and constantly bicker whenever they see each other, but their relationship begins to change when they enter high school!?

(Source: MU)