Mayu is pursuing the mystery of her older sister who went missing two years ago. A trace amount of a man's semen was left behind at the scene where her sister disappeared...Mayu believes that if she can find a man whose sperm matches the only clue left at the scene, she will be able to find the culprit and mastermind. In order to ingest the semen, Mayu becomes the "Phantom Kate" to wipe out the darkness of sex crimes. Her only target is sex offenders! Wipe out the sex crimes that are rampant in the world!