A boy with a short fuse, found almost always mistreating his little sister, Kana. Whenever he is upset by anything, the first thing he does is beat Kana. A later chapter reveals that Jun's mother died giving birth to Kana, which would explain his hatred toward her. During Kanji's story arc, Jun reveals to him that he did not sign the contract.
In the anime series, not only is Jun a pilot, but it is later revealed that he is the orphaned son of Misumi Tanaka and a deceased Yakuza heir. After Misumi's death, Tamotsu reveals to him about his origin, and after Kanji's battle, Coemushi asks him to convince Kana to sign the contract, in exchange for becoming the very last pilot, who according to the rules, has a chance to survive the battle if winning. However, Jun decides not to involve Kana in the contract, and asks Machi to help him. After Machi's victory, Ushiro demands Seki let him become the next pilot and destroy Zearth after winning, relieving both of the successor's duty. After a long 30-hour battle, Jun manages to defeat his enemy and save the Earth for good.
Jun is featured as a character in Bokurano Alternative.