I am Rimuru-sama faithful shadow. I will perform any instruction that I receive.


Souei (蒼影(ソウエイ) Sōei, lit. "Blue Shadow") is a Dark Spirit Oni and a loyal follower of Rimuru Tempest, the King of Tempest.


He’s strange. After being appointed as a ninja, he took the position a tad bit too seriously. His presence radiates composure and unblemished strength. He ruthlessly doesn’t interpose personal feelings.

Being commanded fills him with the highest of pleasure.

Souei has an eloquent tongue to match his good looks.


Souei has darkish skin, dark blue hair, blue eyes, and a height of 190 cm. For a monster, he has a rather slim build. He is a beautiful man with a different air around him.

In the web novel Souei has two horns.


A time of peace had continued for a while. Symbolizing strength, the Ogres had no opponent in the forest. Even lesser dragons had not caused any commotions. He had thought that the peace was a good thing. However, they also wanted to use the skills they have obtained, such was their earnest wish. Then, they were attacked by the Orc army. He could do nothing at all, and left without avenging his lord and fallen comrades. Under the new Lord, Rimuru, he was given the name Souei, and an opportunity to avenge his former lord.


He excels in spying and information gathering. By creating clones, he can get some sleep in shifts.

Though Rimuru taught him the basics of being a ninja, he developed it to suit his own tastes. The most important points were taught by Fuze.

Souei is currently studying torture. Souei can stimulate one’s erogenous nerves with a thread. Rather than pain, a heavenly pleasure attacked them. In addition, he seals their ability to faint. If the target doesn’t talk he or she will go mad.


  • Darkness spirit magic

Ultimate Gift

  • Shadow Moon Lord Tsukuyomi
    • Thought acceleration
    • Eye of the Moon
    • One Hit Kill
    • Ultra Speed Movement
    • Parallel Existence
    • Space manipulation
    • Multi-Layered Barrier

Unique Skills

  • Assassin: (Integrated into Ultimate Gift Shadow Moon Lord Tsukuyomi)
    • Thought Acceleration
    • One Hit Kill
    • Supreme Acceleration
    • One Hit Kill is not a physical attack, it targets the spiritual body directly. So if they aren’t guarding their soul, it can’t be protected against.

Extra Skills

Daily Skills

  • Universal Perception
  • Stealth
  • Fear
  • Majesty

Battle Skills


  • Physical Attack Immunity
  • Natural Elements Immunity
  • Abnormal Status Immunity
  • Mental Attack Immunity


Souei received two ninjato forged by Kurobee.

Souei does not wear armor. Instead, he wears a chainmail woven from Rimuru’s steel thread, which was built for agility.


  • Benimaru: Benimaru and Souei are rivals and best friends. For Souei, Benimaru who is son of the lord was not his lord. Similar of age, Souei treats him as a rival. Someday, he considered to serve under him, but it was not meant to be. Instead, they began to serve a lord named Rimuru.
  • Grenda: Souei sees her as a nuisance.


Tensei Shitara Slime datta ken Wiki has a collection of images and media related to Souei.