
I’ll reply, he’s the child whom MC saved back in the days. ML was the only survivor in that area. After that, MC used to visit him regularly at the hospital, this visitation gives motivation for mc to keep on working hard (back then mc was deemed a hero and everyone took him for granted. Everyone made him work nonstop to the point of exhaustion. Even regular hunters got lazy in dungeons since they all claim “J can do this much faster, why are we wasting our time?”)
Its really heartwarming tho and mc even claims ml as his only “success”, probably meaning the only person he ever succeeded in saving

yeah, like they said. ML was kidnapped after mc went into the rift, and was experimented on by "Prometheus" (an organization which is trying to make false awakeneds, through drugs). they have all failed though, and ML awakened after being experimented on.
so, yeah, they did know eachother; quote from the book: "Lee Sa-young. Cha Eui-jae’s only success".
Can I have some spoils ?