In the future, monsters living amongst humans will begin wreaking havoc, but humans with superpowers will emerge to combat them. One however stands above all else: The Slayer. This hero is seemingly unstoppable, able to No-Sell all attacks. She only has one goal: To wipe out all Monsters, and she's even willing to demolish civilian areas if it means getting to the Monsters hiding there. For the Monsters, it seems like extinction is the only option. Until Kang Tae-Gu enters the scene.
Kang is a Monster-human hybrid with a powerful regeneration ability. This makes him the only person able to survive the process of going back in time. The only remaining monsters task him with traveling to the past, infiltrating the Slayer's high school, and killing her before she becomes the Slayer. Things become more complicated when the Slayer, Eun Ji is already a top student at their school for heroes in training and able to shrug off most of Kang's assassination attempts. Things only get further complicated when she falls in love with him.
This work contains examples of:
- Abusive Parents: Eun-Ji's parents put her through Training from Hell upon noticing her potential, both in the hopes of becoming the head of the Heroes Association if they're credited with her success.
- Child Prodigy: Eun-Ji showed signs of great power from early childhood, so her parents decided to hone it by putting through Training from Hell and having her take experimental performance enhancers.
- Distressed Dude: Kang is kidnapped in chapter 15.
- Genre Savvy: Tae-Gu eventually figures out that something traumatic will happen to Eun-Ji to make her hate monsters, and decides that taking advantage of her crush on him to keep her out of trouble is a better course of action than killing her.
- Half-Human Hybrid: Tae-Gu can pass for human because of this. This is just a cover story so he doesn't get ostracized by the Monsters. He's 100% human, and is siding with the Monsters because his parents were killed by the Slayer when some Monsters thought that hiding amongst civilians would keep her at bay.
- Heroic Sacrifice: Kang's parents sacrificed themselves to save him during one of the Slayer's indiscriminate rampages.
- No-Sell: The reason why Eun-Ji's untouchable even when she's in high school.
