Summoned from another world through ritual, Ryota Sekiguchi was rescued by Yuuki Kagurazaka and placed under Shizue Izawa's care in Freedom Academy's Class S. He learned his body couldn't fully contain the summoning's magicules, condemning him to live only a few more years. After Shizue Izawa's departure, Ryota and his classmates resisted new teachers until Rimuru Tempest took the role. Ryota joined a class challenge against Rimuru, flying into a berserker rage when angered before being quickly defeated. Rimuru then took the class to the Dwelling of the Elementals within demon lord Ramiris' dungeon. Praying at an altar there, Ryota attracted lesser water and wind elementals. Rimuru synthesized these into a dual-element greater spirit, stabilizing the rampaging magicules within Ryota and securing his survival. During an outdoor training session supervised by teacher Tiss, Ryota and classmates used a camping car provided by Rimuru. They were ambushed by thieves, whom they defeated, only to later confront a powerful specter allied with the thieves. Facing dire peril, they were saved by the primordial demon Noir, who intervened in response to Tiss's summons. Ryota and his class expressed sadness when Rimuru announced his teaching departure but promised to maintain contact, with Tiss becoming their permanent instructor. Later, visiting Tempest for a festival, Ryota discovered Rimuru's true nature as both slime and demon lord. He formed a friendship with Hinata Sakaguchi during this visit and attended the martial arts tournament as an audience member, sharing meals with his class during breaks. Physically, Ryota appears as an average middle-school-aged boy with black hair and blue eyes, wearing the standard Freedom Academy uniform. His personality is generally timid but displays intense aggression when provoked.