Seigo went to work in the Philippines for a while and suddenly returned to Japan. During his absence, his brother was also married, and when he met his sister-in-law, Seigo was surprised that she was his ex-girlfriend! That night, Seigo accidentally discovered that his brother and his wife were having sex, and through his sister-in-law's expression, Seigo knew that this ex-girlfriend was not satisfied. It's been a long time since she had been fucked, but witnessing last night's incident made Seito's sexual desire rise. He risked fucking his sister-in-law even when his brother was right next to him. Although she couldn't speak, her sister-in-law only prevented her superficially. Even after Seigo had ejaculated, she actively wanted him to fuck her again, and this time she wanted him to cum in her pussy! And since then, the two have been constantly secretly fucking each other right next to their brother who is always devoted to his family...