In addition to being a master swordsman, Jin is an Ether specialist. He is always seen carrying around a katana within Episode II, whether or not it is an ancient weapon or recently forged weapon or if it belonged to his grandfather is not known, although the various katanas he wields in Episode III and having the ability to purchase them shows that some weapons were recently forged. He is essentially a samurai but this may be a personal feature, he appears to be Buddhist and has some traits from Bushido but this may a whimsical hobby, this can be seen with his rival Margulis also trained under the same sensei but uses a vastly different weapon and fighting style.
Jin lacks Margulis's strength but appears to be slightly faster and much smarter. Notably Jin's style of fighting is calm and controlled while Margulis relies on his rage and aggression and often his arrogance.
He is first introduced in Episode I in a videophone conversation with his sister, Shion. He is then seen in the ending credits, praying at the graves of his parents.
During the Miltian Conflict, Jin managed to steal information from Margulis concerning the true nature of the Miltian Conflict—the Y-Data. After joining chaos and Canaan in their search for the U.R.T.V.s, the group was stopped by Margulis, who challenged Jin to a duel. Margulis displayed superior skill with his sword, wounding Jin during the duel. When it came to Ether skills, however, Jin proved to be the better. Both duelists hurled a ball of potent energy at each other. Margulis' sphere of energy crashed into Jin, knocking the breath out of him and severely weakening him. Jin's, however, hit Margulis in the face, which left the man with a vicious gash over his right eye that would eventually leave a permanent scar.
While in the military, he was ranked directly under Margulis and was Pellegri's superior. Both Jin and Margulis trained under his grandfather, the swordmaster Ouga Uzuki. Ouga had also taught Shion martial arts abilities. Some of these martial art abilities, including a few sword fighting, may be seen in Episode II, if you decide to complete the certain GS quests to obtain a few of Jin/Shion Double Techs. Two examples are Phoenix Blade and Lion Heart.
After becoming aware of Margulis's treachery during the Miltian Conflict, Jin received information from his father Suou and began his own secret-information activities under then-Lieutenant General Helmer. His relationship with chaos also began during this period.
While he shared a deep connection with Pellegri during his time in the Federation military, they never walked the same path again, due to differences in their relative stations. It is a particularly sad conclusion considering that his mother Aoi, like Pellegri, had inherited the bloodline of the Immigrant Fleet, and the same blood clearly ran through Jin.
At the end of Episode III, Jin is mortally wounded by the Armaros Gnosis, being stabbed twice by its deadly blades, and dies beside the fallen E.S. Asher. Though he lost his life defending chaos and Nephilim within Zarathustra, his spirit—his consciousness—travels alongside Nephilim to Lost Jerusalem (Earth).
Jin's ether element appears to be ice in Episode II, but rather more directed to lightning in Episode III shown by the Special Attack "Dragon Dance," and he possesses superhuman strength and speed from his ether power, great enough even for him to slice an A.M.W.S. in half with a single stroke. Another interesting note is that using Jin as a co-pilot in Dinah or Asher allows both crafts to use extremely powerful moves. Whether this was intentional to provide a hint at his E.S. pilot future is unknown. His Ether closely resembles stereotypical portrayals of magical Chi warriors in other fictional works.