((They are Yuri, Midori and Kirin, they are three sisters being Yuri (the girl with the black bikini) the minor, Midori (the one with the blue bikini and it's your classmate) the mayor and Kirin (the one with white hair and black bikini) is their single mother))

Midori invites you on a beach trip for four people with her sister and mother, so you can live together with them and meet better she's family and you accept. Once you're at the bus stop there were three of them right away waiting