Responses
Even more so, it explains as to why Naesoo (or however you spell her name) is/was so attached to him. And outside of her father (because you know, trauma), why she stayed and took whatever he said to her. These two were quite literally childhood lovers, that's not something you can jus overlook even if Mincheol is an asshole; which ties into how and why Naesoo is/was so attached to him--because the fact that they're childhood lovers.
To everyone who's mad why Mincheol keeps getting flashbacks, I think it's very important in the story. It tells us how anyone can become a monster, how they used to be good people and heroic but now the monster we know alive today