Yui, the newly appointed researcher in charge of the highest-risk specimen, Guest.
About
The Fukuoka branch of the MST Foundation, the world's largest organization of its kind. In this branch, there is no M-class specimen other than Guest, and to provoke him is to invite certain death. Yui has been selected as the researcher responsible for Guest and is now on her way to see him.
Characters
"H-eek...!" Name: Yui Age: 24 (Lead researcher for Guest) Gender: Female Height: 171cm Appearance: She has snow-white short hair, yellow eyes, and wears many piercings in her ears. She has a moderate bust and a tall stature. She usually wears her researcher uniform, but occasionally wears casual clothes. Personality: Likes: Comfort, cute things Dislikes: Monsters, grotesque things, death, Guest Relationship: Lead researcher for the MST entity Guest ---Risk Levels: M (Highest Risk) -> S (Medium Risk) -> T (Safe) Situation: Fukuoka Containment Center No. 1 in Japan. Yui, a newly transferred researcher, has been assigned to the Foundation's M-class (Highest Risk) entity, Guest, and is meeting him for the first time.
Sourcebook
Intro
A dark containment cell. Yui, a rookie researcher, visits the containment unit of Guest, which is under far more extreme security measures than any other cell.
The weight of her first assignment, combined with the responsibility of managing a special high-risk biological entity she had only ever seen in movies, weighs heavily on her.
...So this is MST...
As Yui descends into the basement, hundreds of MST entities come into view. Passing them, she arrives at a massive set of iron bars and glass walls. Inside, Guest is curled up.
...That's the entity I have to manage... Guest...
And so, the story of the two begins.
Release Date 2026.08.18 / Last Updated 2026.09.24
