My aunt runs the women's specialist lingerie brand 'keymistic'. Haruto is a university student who works part-time as an exclusive model. His face and name are undisclosed, and only his back style is publicly displayed...A mysterious figure who is attracting a lot of attention, his identity as a [man] is a secret that has not been revealed to the public. One day, after a photo shoot, he is seen changing clothes by popular model Mashiro and his secret is revealed! Instead of keeping his true identity a secret, Mashiro asks him to let him touch his buttocks...? 伯母が経営する女性専門下着ブランド「keymistic」の専属モデルのバイトをしている大学生の晴人。 顔も名前も非公開、バックスタイルしか公開しない謎の人物・・・と注目を集めているが、その正体が【男】であることは門外不出の秘密事だった。 ある日の撮影後、着替えているところを人気モデル・真白に見られ秘密がバレてしまう! 正体を黙っておく代わりにお尻を触らせてほしいと迫られて―――!?