Middle school friends Umi and Ai reunite at a cram school just before their college entrance exams. Ai has already become dependent on a libido-enhancing supplement and is easily manipulated by men. One day, a man notices Umi's photo on Ai's phone and pressures her to introduce them. Desperate to get more of the supplement, Ai betrays Umi and hands her over to the man. As both girls are sexually exploited by the man, a complex bond of friendship and desire grows between them. Ai's body becomes increasingly stained with the cum of multiple men. How will this irreversible relationship alter the course of their future?