Mirajane

nothing much info about him I think this was the 1st time he was detailed in the story so far

He was a manager assigned to him by Nympha, his company. It's implied that he was basically the first ever true friend he had and the only one who could handle him, but for some reason he ended up leaving the professor. Everything after this is a spoiler so don't read if you don't want to.
I'm caught up on the raws and there's still not much information about their relationship, the only things we know about his personality is that he was warm like Garam. Eva remarks upon this, saying that despite the professor getting warmer from Garam's influence, Garam is getting colder (though ngl most times he's actually justified so I disagree with her and think he's just maturing), just as in the past the manager also started getting colder by interacting with the professor too much, so that could be part of the reason.
The professor remembers clearly their time together, but cannot at all remember his face and he goes out of his way to ask Talinski for pictures of him, but there's none. It's also known that the manager died in a supposed accidental fire. He keeps haunting the narrative up to chapter 201

Thank you so much for telling me!!

Where do you read the raws?

I tried to get as many free chapters as possible combining both lezhin Korea (1 episode free every 2 days through the daily log in event) and comico.jp which gives 2 free chapters a day (24 hour countdown which is story exclusive + 1 free ticket per day). After that I just bought 166 coins from lezhin Korea which was enough to finish all of the episodes and have some leftovers for following chapters too.
Little life hack I used was also opening up the raws on my laptop and reading them by using Google translate on my phone, so I would point the camera on my laptop screen while I was scrolling so that it could translate it quickly and I could scroll past, rarely the translation didn't make sense but I'm pretty sure I managed to understand good part of the dialogue and story

That’s actually pretty heartbreaking

Did they go all the way in the raws?

What do you mean? if you mean sex then yeah they have a pretty active sex life. If you mean going all the way with the previous manager then no, it's implied they were only friends.

I mean him and garam will finally having sex as in penetration in the raws?

yep, dw it'll happen pretty soon for the first time, after that they can't keep their hands to themselves ever again lmao

21-22 for han haram and def 40+ for kim heejae

I think Garam is actually younger.
The setting up to the latest chapter here is 2019.
Professor was born in 13 February 1978, so he should be 41.
Garam was born between 1999-2000, so he's either 19 or 20.

Yeah you’re right! I just thought that I read a page where he himself or someone else mentioned his age of 21(?) but it can be my imagination then

Garam's age is actually unclear until very recently.
It was only in the latest chapter 201 where it's implied.
I believe he's 20 tho, the way he's already drinking alcohol could be a hint?

The translator mentioned that garam was born in 1999 and haejee in 1979, it was mentioned in the earlier chapters when haejee was born, since the story took place in 2019-2020 it means garam is 20-21 and haejee is 40-41