Jun Inoue, a second-year Ryuumonbuchi High student, stands at 183 cm with short grey hair and grey eyes. She wears the male school jacket with a skirt, loose tie, and sneakers. Tomboyish, lazy, and pessimistic, she often uses cynical or snide humor yet firmly corrects anyone questioning her femininity. Despite her laid-back nature, she displays sharp analytical skills during mahjong matches, accurately deducing opponents' strategies. She maintains a close bond with Koromo Amae, frequently comforting her during distress.

As her team’s vanguard, Jun specializes in manipulating the game’s flow by strategically calling tiles to redirect them from opponents while accepting unfavorable draws herself. This tactic disrupts opponents' hands and enables massive point gains—over 100,000 in two hanchan. During the prefectural tournament, she dominated early by countering Yuuki Kataoka’s advances but faltered against Mihoko Fukuji’s analytical eye, suffering repeated losses. Though frustrated post-match, she admitted enjoying the challenge. Her flow manipulation later failed against Nodoka Haramura in the individual tournament, eliminating her.

Within Hajime Kunihiro’s familial team structure, Jun embodies the "father" role alongside Touka Ryuumonbuchi as "mother," reflecting her protective and occasionally authoritative dynamic with teammates. She initially opposed attending the combined training camp, deeming it inconvenient, but relented when Koromo showed interest. There, she rematched Yuuki and discussed Touka’s exceptional performance with Koromo, preferring Touka’s usual self over her competitive persona.

At the national tournament, Jun supported Kiyosumi from the stands while accompanying Koromo daily, noting oddities like a mysterious figure in black. She later recognized Yuuki’s refined tile-calling techniques honed at camp.

Trivia notes her surname meaning "well/upper" and given name meaning "pure," alongside her poor artistic skills revealed in Saki Biyori.