The moment he gets a girlfriend, his jealous tsundere childhood friend MIA invents a bizarre rule: three seconds of penetration does not count as cheating. Claiming the virgin needs kissing and sex practice, she pulls him into daily short-time sessions that quickly escalate. What begins as practice reveals their incredible chemistry, and soon he is the one begging for those three seconds. Repeating the countdown as they climax again and again, the pair cuddle and fuck with growing intensity—until three seconds somehow feels much longer than it should.