Shota has long harbored a strong interest in the big breasts of his childhood friend's older sister, Shiori. Drawn to her massive bust, he constantly fantasizes about her—initiating wrestling games, inviting her to bathe together, and pretending to check out her swimsuit just to sneak peeks at her ample cleavage. Fueled by intense desire, Shota plays naughty pranks on Shiori, whose J-cup breasts captivate him completely. His bold advances and growing affection unfold like a romantic drama, bringing unexpected changes to their relationship.