The MC blames himself for being stabbed (and abused) (I know MC made mistakes but seriously a victim blaming himself for every fucked-up sh*t...). He also thinks probably that he deserved being abused and stabbed bc poor uwu Heeseo had suffered enough bc of him and his mother, and at the end simply decides to go back to poor uwu Heeseo bc he's the only victim in this mess... Or something like that... ¯_(ツ)_/¯ A very poor attempt to justify the relaitonship and end the story quickly.
Where tf did you get that Tae-kyung blames himself for being stabbed? If you read between the lines, he felt angered by a lot of things blames himself for doing things differently in the past. Directly blaming himself for getting stabbed is different from that.
Wait what
Can someone explain what just happened in this chapter, I have no clue if I understood it correctly at all. But one thing I did understand is that MC fucked up his life by going back to ML