Taboo Charming Mother (2003)
A wife has an affair with her stepson.
while husband is at work
Netorare: Tanabe Yuuka no Dokuhaku (2010) aka Cuckold: Yuuka Tanabe’s Monologue
A wife gets graped by a guy inside her home while her husband is at work. It gave her pleasure so the next time the guy comes to her door, she invites him in and screws him willingly.