>>2713834It's a one shot.
A small group of friends and family members, most of then at mid age, save for one girl and one girl who have never met each other before, spends a few days on a cottage near a lake.
They get to meet each other, and some of the other people as well. Some slice of life scenes with interesting dialogue happens, they start to know each other interests, hobbies, personality, professional life, struggles, etc.
The closer they get, the more sexual tension there is. Since they're on a cottage near the lake, they eventually start wearing swimsuits, and eventually when they're alone the girl starts getting touchy, and eventually they start fucking. Then there are more slice of scenes later that quickly turn into ecchi then sex scenes too.
They live afar from each other and have busy lives, so they're not a couple yet, but they get each other's number before leaving.