High school freshman Mamoru Kishino sits just in front of Koko Oshii, the most beautiful girl in his grade. He admires her from a distance until one day he accidentally witnesses her losing control of her bladder. He discovers that Koko suffers from an extremely weak bladder, causing her to have urgent and often uncontrollable needs. Embarrassed and desperate to keep her condition a secret, Koko reluctantly accepts Mamoru’s help. He vows to protect her secret and her bladder at all costs. Their daily school life becomes a series of tense, comedic, and often awkward situations as Mamoru tries to anticipate Koko’s needs and find her a restroom before it is too late. Koko, who initially appeared aloof and harsh, gradually shows her true, more vulnerable personality. The story also introduces a mysterious class president with long black hair who becomes involved in their predicament. The manga blends romantic comedy and ecchi elements, focusing on the unique bond formed between the two as they navigate Koko’s condition and the chaotic moments that arise from it.