Omg i nearly suspect that Mr Kim is Sejun's dad since he care for him more than anyone else. Did Sejin knew about his biological parents in the end?
No, Ido won't tell him. At least that's what i got from the novel (i used auto translate).
And Mr. Kim is not that much older than him, they're more like siblings. He's Sejin's guardian angel.
I mean, Sejin is a really likeable and friendly individual. befriending him and caring for him would come naturally. Kind personality tends to attract kind gestures.
You really have to be something else to treat this Cinnamon roll like trash.
The worst part is... Sejin is the son of a wealthy couple but his parents died in an arson and he was kidnapped. He has no memories of this, he thinks the guy who kidnapped him (who he ran away from in that cold night) is his real parent. The guy who adopted him also knows this but kept it a secret. Unfortunately the author doesn't delve too deeply into this story. Ido investigates it but he also keeps it a secret from Sejin because he doesn't want Sejin to get hurt anymore.
Poor Sejin could have everything but he's had the shittiest life since he was an infant. He tried to get away from a bad (fake) parent only to fall into the hands of an equally bad one.