After missing the last train, my girlfriend's adult sister Kanna suddenly turns up at my home. Her relaxed loungewear, fresh smile after a bath, and casually exposed natural breasts make resistance impossible. She teases me for staring, admits she wants me, and draws me into affectionate forbidden sex while whispering that it must stay secret from her sister. We kiss, lock eyes, and make love again and again until she promises to overwrite every memory I have of sex with her sister.