Soichiro Kamui is a young city council member with a promising political future. Ten years earlier, during high school, he achieved legendary status as the only player to conquer the notoriously difficult full-dive RPG "Kiwame Quest" (or "Extreme Quest"), earning the in-game title "Eternal Invincible Adventurer" under the player name "Kamui".

He possesses medium-length, messy blue hair, deep blue eyes, and is often described as handsome. During gaming sessions, he typically wore a charcoal black hooded sweater, gray pants, brown shoes, and concealed his face with a distinctive crow mask.

As a politician, he exhibits a calm, soft-spoken demeanor. This contrasts sharply with his behavior during his gaming career, where he displayed a brutal and disparaging attitude. After completing "Kiwame Quest," he authored the comprehensive "Oberdine Chronicle," a strategy guide documenting exclusive tips, tricks, and secret techniques (cheats). Despite its critical value, the guide is characterized by harsh language, insults, and generally unhelpful commentary. His motivation was to share his knowledge, albeit confrontationally.

He demonstrates mastery over rare in-game "secret techniques" (cheats) and occasionally manifests as a ghostly apparition to provide guidance to Hiroshi Yūki during challenges. Beyond gaming, he established a strategy website notorious for its abrasive tone rather than practical utility. His rejection of Reona Kisaragi a decade prior, citing disapproval of her appearance, indirectly influenced her later actions involving Hiroshi Yūki.

The etymology of his surname Kamui combines "神" (kamu, "god") and "居" (i, "residence/dwelling"). His given name Soichiro incorporates "宗" (so, "religion/sect"), "一" (ichi, "one"), and "郎" (ro, "son").