Natsuki, living with her stepbrother who attends cram school. Her stepbrother admires her and begs for 'just 10 seconds' of insertion, but it's too much of a perfect match and her pussy immediately orgasms! She knows it's wrong... but her hips and libido won't stop, seeking each other again and again! Whenever there's a chance, 10 seconds... another 10 seconds of frantic mating! The originally pure Natsuki-san's climax appearance