Hi , then the thing i remember is , there is the girl and man are in high school and they have the best notes but the man is always better, they make the bet the one who win the next test will do anal sex to the looser and the girl loose, don't remember more.
Thx to help

I think it's:
Wise Ass - http://www.mangaupdates.com/series.html?id=33095

Remembrance, a forsaken thing that revokes ignorance and leaves people in doubt, is my only redemption and solace deep within the cascade of white.

The evergreen trees speak of days long past when music mingled with the wind and sweet murmurs brushed our cheeks.