연쇄살인마가 우리 집에 들어왔다

A love story between Risa Shiroki and Hiroto Fukami. Twenty year old Risa Shiroki comes to Tokyo from her hometown in the countryside to attend university. Pretty and popular with male students, she has never had a boyfriend and dreams of having a sweet love. One day, thirty year old Hiroto Fukami appears in front of her. He is business man who appears to be gentle and looks perfect. As romance blossoms between them, Risa discovers Hiroto's dark past.

In the world only the aristocrats have the power to fight the monster - mana. Even though Melida Angel was born in an aristocracy and studies at an academy developing mana users, she has no mana. To find her talent for mana, Kufa Vampir was sent to be her tutor but at the same time, he was ordered to assassinate her if she has no talent for mana. He makes a cruel decision to assassinate her because he thinks that it is a wasted effort that people who have not any mana are working hard in this world... However, he asks her, "Do you want to try to entrust your life to me?" He is not as an assassin nor a tutor. He is someone betting on his pride as an assassin tutor, to show the world what Melida is capable of!

The series is about an incident that takes place when the owners of the boarding house called 'Guest Summer Palace', which breaks stereotypes, and boarders with secrets gather to find Lee Seol who disappeared 13 years ago.