
I think he is an older guy compared to mc, he went to school as a hunter and gained fame and power easily with an ss class revealed before he even entered the esper school. Lost Ano as his previous guild that was American failed to succeed at the SS class dungeon and went under disguise to regain his strength in Korea to stay and one day redo the dungeon.

It makes sense from the MCs perspective, once you know his backstory you'll. Also keep in mind that ML established early on that the relationship was just a game for him, then during the guiding he said he was just using MC when MC asked him. He has gone out of his way to make sure that MC doesn't think there's any feelings there, because there wasn't. Then when he catches feelings he makes no effort to clear it up and let MC know that he cares about him.
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MC has a history where an Esper was obsessed with him, did not care about him in the slightest but was obsessed when MC was 14. That guy kept him captive and locked up for years, he's the one that marked MC over the heart so MC couldn't leave. If a marked guide severs their relationship with the Esper who marked them they get a painful debilitating backlash from it. It's usually not done anywhere that might cause the backlash to be deadly, like over the heart, so as long at that guy was alive he couldn't leave or it would kill him. When MC keeps thinking about how he doesn't want to see anyone die from needing guiding again, it's because he refused to give guiding to the obsessed abusive guy and watched him die. Due to ML being who he is, MC is hurt and runs away thinking the ML doesn't even care. When ML shows up after finding him, he's terrified that ML is just obsessed with him because of his guiding ability and will do anything to keep him close, he's afraid of being imprisoned again.

Owen became an SS-class at the age of 17 and his fame only lasted for about around two years. because when the SS-class dungeon appeared, LEOM, his guild that time, went in and failed, which caused them to disappear from the world. then, later on (not sure how long tho), LEOM re-emerged in Korea but already assumed different identities, which is why he's already been known as Andante from there on, when he attended the training school with Shin Haechang and Yujin. Then, 10 years later, the SS-class dungeon re-appeared in the current timeline. So, Andante's most likely already 29-early 30s, while Hyoseop is 24-25.
Dude, his timeline makes absolutely no sense. Then is he actually way older and went to school with a diff identity? Did he pay off the school to hide his class. I don't know and I don't care about him enough to investigate myself