Zettai Oshienai(2008)

Zettai Oshienai

Sugiyama Rika is the Chief of Public Moral in her school and dislikes the school's student body President Jinguuji Kasui. She thinks he's incompetent and an expert at lying. One day a rumor broke out about a myth about love in their old school building, suddenly Rika finds herself entangled in the love myth with none other than... Jinguuji Kasui?!
(Source: Wataame Shoujo)