A young boy who lost his mother when he was very small. He practices Kendo every day because his goal in life is to become strong. He is always defeated by his rival Mirai Kaname.

Due to family circumstances, Setsuna Kai is moving to a new city where he's supposed to live by himself in an apartment. As soon as Setsuna arrives, he witnesses a mysterious rain of rocks and barely escapes being crushed by an enormous boulder. Setsuna's new home wasn't as lucky, being completely destroyed by another giant boulder. Setsuna is distraught, not knowing what to do when he's approached by a scientist named Hiromi Kaname. Dr. Kaname's equipment apparently can tell that Setsuna is a "Devil Child", and so Dr. Kaname decides to take Setsuna to his laboratory.

**Height:** 165cm 
**Favorite color:** Black
**Graduated:** Meiji University

**[Artist Profile (Add9th)](https://add9th.co.jp/profile/)** | **[Twitter](https://twitter.com/MorikuBorn)**

Shoutarou Morikubo is a Japanese voice actor who has been active in anime, drama CDs, and video games. He's the founder and representative director of [Add9th](https://add9th.co.jp/). He has additionally released song singles, a CD album, and a concert DVD. He was formerly affiliated with I'm Enterprise and VIMS.

In 2018, he formed the musical unit [buzz☆Vibes](https://anilist.co/staff/160730/buzzVibes) with Japanese multitalent [Shinnosuke](https://anilist.co/staff/160731/Shinnosuke).

At the end of the 20th Century, the world is facing destruction from massive earthquakes, bad weather and other abnormal phenomena. In Tokyo, Setsuna Kai, a young boy who lost his mother when he was very small, practices Kendo every day because his goal in life is to become strong. As always, his rival Mirai Kaname defeats him and Setsuna feels sad. On his way home, a messenger from the Devil's World appears before him. This messenger proclaims that the various abnormal changes in the world are the work of the Devil. The world will come to an end unless the Devil is conquered. The only ones who can save the world are the "Devil Children." Thus begins Setsuna's adventure in the Devil's World -ANN