Shota, who was still a virgin, finally met his long-awaited girlfriend. Upon learning this, his overprotective mother, Kei, decided to teach him how to kiss and pleasure a woman properly, so her son wouldn't embarrass himself. However, Kei's sensual gestures unexpectedly aroused the innocent Shota, causing him to become increasingly erect. Noticing his arousal, Kei hesitates, but when Shota pleads with her to let him go all the way, she finds herself torn. A new, forbidden relationship begins to blossom between mother and son.