Groper Train: Packed to the Brim (1981)

Original title: 痴漢電車 奥までつめて

A young woman was on the train heading to a seaside guesthouse to enjoy a relaxing summer vacation. She was molested on the train. When she arrived at the guesthouse thinking that it was the start of her unlucky vacation, it turned out to be an old-fashioned inn run by a widow. On top of that, the previous guests, an adulterous couple, were in the middle of sex, yelling loudly, not caring about the sea. The widowed landlady was masturbating while peeking at them. It was even more unlucky. She became depressed. Then a new guest arrived. She was surprised to see the man. It was the molester from the train earlier...