Hentai Ouji to Warawanai Neko.

Yokodera Youto is a second-year high school student who is arguably the biggest pervert at school. His problem is that he is not good at showing his real emotions. One day, his equally perverted best friend completely transforms and gets rid of his "impure thoughts"; a feat he attributes to the power of the statue of the "Stony Cat". As the rumors suggest, by wishing upon the statue and giving it an offering, one can wish to remove a personality trait from themselves that one does not wish to have anymore. However, this will remove the unwanted trait and give it to someone who does need it.

As Youto is making his offering to the statue, a girl named Tsutsukakushi Tsukiko arrives to make her wish to be able to be more like an adult and not show her emotions so easily. Both of them wish upon the stony cat and to their surprise the next day at school, Youto is unable to tell a single lie, and Tsukiko is unable to show any sign of emotion whatsoever. After realizing that they do not like the change that happened, they work together to try and find out who has received their trait that was taken away in order to get it back. They meet Azuki Azusa, an attractive second-year girl who has just transferred into their school. She is always being confessed to by many boys in school, but she has no friends and is always alone. Youto finds out that Azusa is the one that received his unwanted personality trait and tries to get it back. As the two try to get back the unwanted trait, they develop feelings for each other.

[Edited from Wikipedia]