Ashiya Souma was experiencing something new in his life. Three girls confessed their feelings for him at the same time, and he was asked to choose one of them from the Ladies' Alliance. And all of the girls have a clear suntan mark. Nago Natsuno is a neighbor girl who moved in a while ago, so contact with her is still limited. He gets very excited by girls with suntan marks. She has a slender body that is appropriate for her age, but her tan is very healthy. However, there is too little fabric, probably because of the summer, and it's hard to look at it! And Natsune is the last of the “Ladies' Alliance” assassins! She may be experienced, but what is she capable of? And will Suoma be able to choose one of them?