Shippai Kinshi! Kanojo no Himitsu wa Morasanai!

Seiryuu Academy, the Second Flower Arrangement Club-- This club that gathers the top beauties in the school is a mysterious organization of unknown activities and admission conditions. The protagonist, Shimizu Shou, due to some strange opportunity, was recommended to enter the Second Flower Arrangement Club by his sister Hijiri, a member of the club.

"Bro-Brother. That stain...perhaps...?"

"That's not it, Hijiri! It's just spilled orange juice!"

...the conditions needed to join the club that are shrouded in mystery are...? Without knowing the reason, Shou, who was waiting in the clubroom for the club president Ryuusenji Kurisu, learnt her secret there...! He must not let this known!! An Outstanding Newcomer Excellence award! A secret problematic work is finally released!
(Source: Baka-Tsuki)