I don’t speak Japanese but it seems to me that the plot goes something like this: An old man brings his daughter/granddaughter/niece (the film is classified as incest porn) to a bathhouse where she and her girlfriends, who for some reason just happen to be there, jerk, suck and fuck older men through a plastic foam wall in a large hot-tub.
The first scene features an old man jerking off while watching a teen girl lather herself with soap, they take turns washing each other and then the girl jerks him off until he cums.
The second scene starts off with two teen girls sitting in the hot-tub while another girl sits close by and shaves her armpits and pussy, they are being spied on by an older man who ends up breaking through the wall and grabbing one of the girls, an angry pool guard arrives and shouts at the girls until two of them leave the hot-tub, the old man and the girl he grabbed start to rebuild the wall until they get bored and she jerks him off and gives him a blowjob, the man then starts fucking her in various positions, another man arrives in the pool and watches them fuck, and finally the old man gives the girl creampie and the desperately tries to wash the cum out of her pussy.
The third scene features a busty girl getting her breasts fondled through the wall by an older man. She then breaks through the wall and gives the man a titfuck until he cums all over her lovely tits. In the end they get caught by the pool guard who gets mad and asks them to leave the hot-tub.
The fourth scene starts off with a teen girl with pigtails showering before she goes to the hot-tub. Soon after entering the hot-tub she starts to make out with a guy through the wall, she then gives him a handjob while an older man watches them. Later on the guys switch and the girl starts jerking off the old man and fingering herself while he fondles her tiny tits. She also sucks the old mans finger alot while she fingers her pussy like crazy. The old man then fingers her pussy a bit while they make out through the wall. Finally the wall breaks and the old man goes through it and forces the girl to give him a blowjob until he cums in her mouth. Afterwards the girl thanks the old man and even bows to him out of respect.
The fifth scene starts off with an older man jerking off while watching a teen girl bath in the hot-tub. The girl catches him and acts surprised but gets too curious and starts to jerk him off as well as sucking his dick. The man fingers the girl through the wall until she cums and squirts allover the place. He then licks her pussy from behind before fucking her doggystyle while an older woman watches them. They fuck so hard that the wall breaks, the man cums in the girl’s pussy and the woman yells at them for breaking the wall and even slaps the girl. After the older woman leaves the hot-tub the teen girl becomes distraught and starts to cry, the man consoles her and they make out. He then starts to lick and fondle her breasts. He also fingers her pussy a bit before she sits on his face so he can lick her pussy well. Finally the man fucks the girl in various positions until he explodes inside her and the girl watches while his cum leaks out of her teen pussy and down her ass.