As an Ogre, Souei had a lean yet muscular figure with a height nearing Benimaru's Ogre form. He has dark skin, dark blue hair and, blue eyes.
From his forehead protruded a single black horn and a blue eye-shadow on his lower eyelids. His skin also had a bluish tint which made his look overall grayish. From the corners of his mouth, also peeks two white canines, which further complements the already vicious and angry Ogre appearance.
His hair was straight and is of medium length, where his bangs covered his right eye most of the time. His clothing is tight-fitting, possibly due to his fighting style relying on speed and agility.
After evolving into a Kijin, Souei shrunk to that of 190 cm and with the appearance of a lean young man in his late teens. He looks incredibly calm and collected, which goes well with his confident personality and is all in all a beautiful man (Ikemen) with a different air around him.
Thanks to Shuna and co., Souei received a brand new attire matching his dark blue color scheme that isn't too tight nor too fluttering to get caught in sharp objects during his espionage missions.
Souei seems to be afflicted with Chunibyo. After being appointed as a ninja, he took the position very seriously - too seriously for some of his companions and coworkers. Regardless, his presence radiates composure and unblemished strength. He operates ruthlessly and doesn't interpose personal feelings. He keeps his delusions only to times of peace and properly makes sure that it doesn't interfere with his work.
Despite some the concerns about his personality, he does his job properly and is very competent, able to create a counter-espionage force within a few months that's able to fend off spies from the Armed Nation Dwargon, though it doesn't seem like he was able to notice the magical observation done by the Sorcerer's Dynasty Sarion, so against purely magical espionage methods he might still require the help of an expert on magical matters like Shuna, Diablo, or Rimuru himself.
Souei has an eloquent tongue to match his good looks and always expresses himself very stoically and confident.
Like all the other survivors of the Ogre Tribe, Souei is also very loyal towards Rimuru and he also keeps up his long-lasting childhood friendship with Benimaru, especially now that Benimaru and Souei are no longer master and retainer and can treat each other more equally in public.
Souei was one of the six survivors of the Ogre Tribe. After escaping from the Orc horde, his group joined Rimuru's Hobgoblin village after an initial misunderstanding. He followed along until the village became the Jura Forest Alliance and later the Jura Tempest Federation, where he settled in as leader of the Shadow Squad that handles the espionage of Rimuru City.