@BookQueen1 yeh, that's why I said mostly. But the boyfriend in that arc was merely one of the characters of that "story" while the ML here in this one is a system's host, which is much more special than normal people.
Imo, this side story is specifically used to call out the bullshit of those "lame, loser dude turned OP and gained a harem" stories, which is different and why it's not included in the main story.
Or maybe the author just like to separate them, I honestly don't know.