My guesses

Just finished rereading S1 for the new season and here's a few guesses I have now that it's my 2nd time reading... First guess is he's working undercover for years either with FBI or a non-government organization, which is why he only came back to SoKor a few years ago and right after coming back he shot to stardom as if he was an industry plant (he's also talented so that helps a lot but his position in this NGO/FBI helped him with resources like his company), the origin of the drugs was Brazil and he canonically came from there, which would back up this guess cuz this means he's following a trail of the drugs and where it's being distributed, cuz this is a whole operation he's handling under the FBI/NGO. Second guess is he's also taken the drugs before but have learned to live with it/bear with it (just like how the doctor explained about dopamine substituting the serotonin) which explains why he's the one being shown when they're talking about it (it can also just be a foreshadowing saying he'll be the one to give it to Jaeyoung and will be the "pilot" of Jaeyoung's dopamine intake), this can be why he's tracking the distributors of the H100, cuz he's taken if before and doesn't want it to spread anymore. Honestly can also be a tie in to one of the doc and manager's convo about always being high on dopamine before, like that's how he met them or he was the reason it was always exciting, cuz he needed dopamine to feel something and this little group with the manager helped. These are the only ones I've got so far and honestly can be put together very easily during the first read but I was kinda confused and drowning in their intimacy during my first read so I didn't pick it up.

Anyways, looking forward to more lore drop and intimate scenes with these two. Seriously, what's with them, they feel so intimate.