Shion Otosaka, the individual behind the digital avatar known as Gentleman, is a central figure in the narrative. As a first-year student at Shadowverse Battle College, Shion initially attends classes remotely, avoiding physical interaction and operating entirely through the eccentric and sometimes arrogant persona of Gentleman. This reclusive behavior stems from deep-seated social anxiety and a fear of rejection, rooted in the belief that there is little about oneself that is truly lovable.

The character's background reveals a history of failed connections. Shion was the original and secret leader of the Sixth Magic club but was rejected by the members due to an overly controlling and data-driven approach to the game. Following this rejection, Shion retreated into the shadows, appointing Shinobu Miki as the club's public-facing president while giving her instructions through a hidden earpiece. This strategy allowed for the dissemination of their extensive Shadowverse knowledge while avoiding the risk of personal rejection. Despite their reclusive nature, Shion is genuinely passionate about the game and sincerely seeks to share their expertise, though they struggle to do so without dictating every move.

The role in the story changes following a battle with Light Tenryu, after which Gentleman leaves Sixth Magic and joins the Seventh Flame club. Even after joining, Shion continues to maintain distance by using the digital avatar. The true identity is eventually discovered by Ren Kazamatsuri and Tsubasa Takanashi at an arcade, leading to a duel where Tsubasa agrees to keep the secret if she wins. Tsubasa's victory and her subsequent decision to honor the agreement forge an important bond that begins to challenge Shion's isolated worldview.

Key relationships drive much of the personal development. The connection with Tsubasa is significant, as she respects the request for secrecy and offers friendship. Another crucial relationship involves Shinobu Miki, as Shion later faces her in a tournament while fearing her hatred for the past manipulation; the subsequent victory and Shinobu's neutral response help Shion realize that bonds may not be as fragile as feared. A rivalry and complex dynamic exists with Grand Master Warden Craft, who criticizes Shion for solitary tactics and self-centered existence. Throughout the series, the support of other Seventh Flame members, particularly the unconditional defense offered by Ren Kazamatsuri, is instrumental in Shion's evolution.

Regarding development, there is a clear arc from isolation to integration. A turning point occurs during a visit to Genesis Island, where Shion gathers the courage to appear in person before the club members and other presidents, abandoning the Gentleman avatar for the first time. Subsequent challenges, including the Shadowverse World Ranking event, reignite anxiety, but the character continues to struggle against it. During the Arc Ruler crisis, Shion disobeys direct orders to confront Warden in a high-stakes battle involving sensory feedback that risks physical pain. By the end of the crisis, Shion overcomes most social anxiety barriers, begins attending school in person, and interacts directly with friends, having fully retired the Gentleman persona.

As for notable abilities, Shion possesses an encyclopedic knowledge of Shadowverse and its standard moves, believing that data is the key to victory. In battle, they employ a Runecraft deck with a Chess theme, specializing in swarming the field with Magical Pawn followers and using spells to deal damage and draw cards. The ace card and primary finisher of this strategy is Mystic King. Shion is also skilled in hacking and spying, using these unscrupulous methods to gather information on others without remorse. Outside of Shadowverse, the character has a fondness for rabbits, video games, and chess, and possesses a Digital Friend named Milady, who later evolves into Milady, Mystic Empress during a critical battle.