I think the food is key point because in the second scene the man laugh to her after eating food. And the bamboo is a factor to arouse her. Engilsh fucking hard
@piyin: nah it's the water the owner of the onsen (guy in p.9) explains that the onsen water naturally has aphrodisic effect and the intervals at which water from the mini-waterfall falls is so identical that people get hypnotized by the sound (lol) - which is why everyone is wearing earplugs.