Hahn Jun-Seok was a liaison officer aboard the USS Prospect from 2365 until 2367, again in 2370, and then aboard the USS Prospect-A in 2371 and 2372. He was also a member of Special Operations and sometimes knonw as Jim.
Korean naming conventions list family name first, given names last. His first name is Jun-Seok.
His appearance is human, but, in reality, he is a Na’arbi undercover agent. His true identity remains a secret to most people.
When he was a boy, his parents and he moved from South Korea to the United States of America on Earth. He had to make new friends, learn a new language and adapt to a new environment. This helped him build trust that other people inherently want to tell the truth. (“Starry, Starry Night“)
This story may or may not be true, depending on when a Na’arbi takes human form, i.e. is “reborn” in each incarnation.
The Na’arbi planted several agents both in the Federation’s and other major powers’ societies. He, working under the guise Hahn Jun-Seok, was one such agent. (“Lady Lazarus“)
Aboard the Starship Prospect
Late in 2366, and early into 2367, he assisted the Prospect crew in attempting to get to the Battle of Wolf 359. Unfortunately, the Prospect arrived too late but pursued a mysterious alien ship transmitting some sort of communications beam towards the Borg cube. After the Prospect disabled the alien ship, Hahn accompanied Captain John Greene and other members of an away team aboard it.
During their time there, the alien ship’s commanding officer, Amila Thon, told the away team Hahn would know of foes worse than the Borg. When other members of the away team asked what Thon meant by this, he denied any knowledge of what she was talking about. Thon also whispered in Greene‘s ear that Hahn wasn’t who he said he was.
Hahn assisted the Prospect crew in the rescue effort at Wolf 359. (“The Burnt Child“)
A few weeks later, Greene assigned Hahn to lead the engineering away team to Goffan IV, with Bryan Radke and Jason Athelstan assigned under his command. The away team’s mission was to improve sensor abilities to accurately detect molocine. This was greatly helped by an away team from the Jenchum Suzerainty battle cruiser Alonia, led by their first officer Methia.
Hahn built up a relationship of trust with Methia, and she and her team began to assist the Starfleet team.
After making great leaps and bounds in upgrading sensor technology to detect molocine more reliably, Hahn asked Methia for assistance in determining if the Jenchum were developing subspace weapons in a secret facility in Enika on Goffan III. Methia was unsure about revealing this information, but, after Hahn revealed the Prospect‘s secondary mission, she revealed the Jenchum testing of subspace weaponry was a failure, with a subspace anomaly opening, killing all the scientists and military personnel present. (“Starry, Starry Night“)
Greene warned Hahn he would have no choice but to transfer him off ship if Hahn continued to overstep boundaries. The Prospect captain attempted to give him a second chance on both Goffan IV and Rychri, the former of which he overstepped the bounds again. For an unknown reason, someone higher up the chain of command kept getting Hahn off the hook. (“Starry, Starry Night“, “Honor Thy Father“)
Later in 2367, Hahn was celebrating his birthday when the Prospect received a distress call. Investigating it, the crew discovered the USS Artemis had not exploded in 2364 but jumped to warp and survived.
An uneasy Captain John Greene sent counselor Daniel Radke, first officer Anne Lansing, security chief George Stratos, Ensign Garrett, Ralf Mendoza and Steven Tedesco to the Artemis. Radke and his escort Garrett attempted to locate bodies, but were instead altered by the M’Tar. Transformed into the Liaison, Radke attempted to assist the M’Tar take control of the Federation, but a battle ensued when Hahn spoiled that plan. Hahn severed Radke and Garrett from M’Tar control and transported them back to the Prospect before the Artemis exploded, dragging him and the two M’Tar into the M’Tar Domain, sealing the portal between the two dimensions.
Greene and Stratos investigated a strange energy pulse emanating from Hahn’s cabin to find a holographic transmission, warning Greene the M’Tar were growing in number and not near extinction. (“Lady Lazarus“)
Neither John Greene nor Starfleet revealed the true facts about the M’Tar to Daniel Radke as per his comments in Star Trek: The Cantabrian Expeditions episode “Catalyst, Part One“. It is assumed Starfleet was keeping this knowledge close to their chests for unknown reasons.
By 2370, Hahn had returned, albeit by unknown means. After the USS Odyssey‘s destruction by the Jem’Hadar in late 2370, Special Operations quickly assembled the Prospect crew and sent them from Deep Space 9 to the Gamma Quadrant to make first contact with the Founders. This mission failed, resulting in the Prospect‘s sacrifice in order to halt a Dominion incursion into Federation space. Captain Greene (the commanding officer), and the majority of the Prospect crew, survived on the saucer section, which coasted back through the Bajoran wormhole to Federation space. Hahn was instrumental in helping the Prospect team survive. (“Pure Massacre“)
2371 / 2372
The Prospect-A was sent, in 2372, to the Gamma Quadrant to find the USS Rutherford after it disappeared, and John Greene commanded this mission. Successful in discovering the Rutherford but unsure in the whereabouts of its crew, Greene ordered the Rutherford destroyed to stop it falling into Dominion hands. Hahn provided key tactical information Na’arbi agents had gathered on the Jem’Hadar, helping the Prospect survive. Battles with the Jem’Hadar saw the Prospect suffer heavy damage. (“Directive“)
Working outside Federation and Starfleet protocols, Hahn visited Dr. Samantha Delaney aboard Dante Station after the Rutherford mission. Once there, he destroyed her folded space drive prototype and all her research materials relating to them, driving Delaney further mentally unstable. (Star Trek: The Cantabrian Expeditions: “An Innocent Time“)
The reason the Na’arbi had Hahn destroy the data and prototype was, after the disastrous testing of the device and destructive battles with the Dominion, the Na’arbi felt the Federation was not ready for the technology.