Explain the event that takes place between Genji and Naishi.

Genji is sleeping with Naishi, a woman in her sixties. Tu no Chujo decides to play a trick on Genji while he is sleeping with her. To no Chujo enters the room in a disguise and draws his sword in an attempt to kill Genji. Genji is afraid at first but realizes that it is Tu no Chujo playing a trick on him. The two of them laugh about it and agree never to speak of it again.