Lots of Peeping: Hot Underpanties of a Lover

覗きがいっぱい　愛人の生下着

Also known as Nozoki ga ippai: Aijin no nama-shitagi, Tomorrow Joe is Alive, Ashita no jo wa ikite iru, 「明日のジョー」は生きてるさ

There was a man, a novelist, who had unavoidably turned his hand to sensual novels for a living, but now made a living out of it. One morning while jogging, he picks up a lighter and cigarettes dropped by a bookstore owner, and decides to deliver them to the store. When there is no answer to the doorbell, he goes to the back of the store and looks in the slightly open window to find the owner tying up a female clerk and engaging in SM play.