TV-Series
Description
Yuuki is a human male standing 165 cm tall and weighing 60 kg, with unkempt black hair and teal eyes. His attire features a black and teal outfit with a blue cape, brown pants, dark brown boots, and a blue belt secured by a golden buckle. A gray sword sheath is held by a red strap, though the strap and shoulder plate were omitted in the anime. In real-world settings, he wears a school uniform: a white shirt, dark blue blazer, grey pants, and black shoes.

His childhood involved close bonds: he grew up alongside Saren Sasaki as a close friend, acted as an older brother figure to Rino Inosaki, and was cared for by Shizuru Hoshino before her move. He befriended Hiyori Harusaki by aiding her reunion with her mother and later met Rei at summer camp, learning fishing from her. He also unknowingly assisted school idol Nozomi Sakurai by hiding her from fans.

Forcibly logged into the game Legends of Astrum via a MiMi device by Akira Mosakuji, Yuuki was guided by the fairy Fio. He discovered his unique ability to empower allies' attacks, leading to his membership in the guild Twinkle Wish. There, he honed strategic skills and pledged to help them reach the Tower of Sol's summit. His personality blended sarcasm, dry humor, and blunt honesty, sometimes perceived as abrasive. He demonstrated protectiveness, notably shielding Yui from an attack by Mana Senri (merged with Minerva), which resulted in severe injury and memory loss. Ameth subsequently sent him to the continent of Astraea with a mission.

Awakening in Landosol with amnesia, Yuuki was found by Kokkoro, appointed as his guide by Ameth. He later co-founded the Gourmet Edifice guild with Pecorine and Karyl. The amnesia erased basic knowledge, reducing his mental state near-infancy; he initially spoke in broken phrases and needed instruction on fundamentals like monetary value and directions. Combat skills were lost, leaving him reliant solely on his Princess Knight ability to empower allies until training with Mifuyu Ogami and Rei. He retained selflessness, however, defending Karyl after learning she was an assassin sent to kill him and Pecorine.

His personality shifted across his journey. Pre-amnesia, he balanced kindness with sarcasm and strategic assertiveness. Post-amnesia, he exhibited childlike innocence, adopting Pecorine's culinary habits—including eating insects raw—and occasionally displayed cleverness, like solving math problems. Moments of his former self surfaced during crises, such as devising a plan to rescue Kokkoro from a giant squid. He later suffered a second, more severe amnesia episode, reverting to a baby-like state before recovering. Yuuki harbored a wish to become a Magical Girl, using his power to transform Shiori and Kasumi into them, often against Kasumi's will.

Key traits include Chronic Hero Syndrome, frequently shielding allies from danger despite physical risks. He forms deep bonds across guilds, unintentionally attracting romantic interest from numerous female characters while remaining oblivious to their feelings. His Princess Knight ability enables Super-Empowering, granting allies Princess Forms or Overload Forms during critical events. Recurring elements include being bitten by animals, serving as a Supporting Protagonist in group-centric stories, and employing sacrificial tactics, such as sacrificing past bonds to reset timelines for his friends' safety.