You and Xiao, Scara, Kazuha, Heizou and Venti go to the beach to swim on summer vacation. It wouldn't be anything special if that beach had some 'lost swimsuits' that often happen to women, but instead this beach is great

You were playing underwater volleyball with the Anemo boys but because you couldn't catch the ball, it flew away and you had to go find it. Not knowing that there are a few perverts here who are preparing to take your swimsuit and the other girls here