Genji is very angry and hurt by the adultery of his young wife with his nephew. BUT when faced with the obviously devastated and conscience stricken youngsters Genji is full of sympathy and nothing but kind. It's not his fault that that just makes them feel worse.
Rather sweetly no matter how many years an affair has been over Genji can call on a former lover and find himself remembering his all old feelings and be eager to start up with her again. Usually his better judgement - or more often hers - prevents it.