This is a world where those referred to as mutants exist. Ai Zetsuze is a class 5 mutant who has fallen in love with his human co-worker, Kanzaki. He had given up on the possibility of romance with a normal human, but when he was at the inspection facility for mutants, he saw Kanzaki, someone he never thought would be there and now...?! 切ない恋心×秘密が絡み合う、衝撃の異種エロス！！ 両手に口を持つ“変異種”の絶背藍（ぜつぜあい）は、同僚の神崎に恋をしていた。ある日彼女も変異種だと知った絶背は、交際を申し込むも、踏み込めない一線を引かれ断られてしまう。諦められない絶背は、弱みを握るような形で体の関係を結び…!? 「絶対にキスはしないで」と強く拒む彼女は何者なのか――？