Kusozako Boukou Oshii-san

The high school freshman Kishino Mamoru was expecting a fateful encounter and he met the pretty girl classmate Oshii Koko, and happened to know her secret. To his surprise, he found out Oshii-san's bladder is super weak...!! To not 'leak' this secret, Kishino Mamoru swore to protect Oshii-san('s bladder).