Damn! One of my favorite aspects of this series is the way previous events are recontextualized the further we dive into the story.
Let me start by saying the flashback in this chapter, while pretty emotional, doesn't tell us anything new about Ji-tae other than the extent of his PTSD in the form of haphephobia (fear of physical contact).
Before crossing paths with Maria, Jitae was doing his best at trying to live a normal life despite having to deal with the trauma of losing his sister and being assaulted by his father. The deeper he gets into the world of fighting, the more his emotional scars become apparent.
However, all the signs of him being a broken child were there from the very beginning of the story. The curveball thrown by the author was that at first, all these things were framed as a positive source of motivation. But now we can see them as clear symptoms of self-loathing and PTSD that are rapidly turning into Borderline Personality Disorder caused by the massive contrast between what he believes in and what he must do in order to find his beloved sister. This plus the notion of him being weak and useless being ingrained in both his heart and mind with every shortcoming, loss or failure.
This chapter also confirms what was previously implied about the loss to Young-joon and the incident with Maria resulting in his breaking point. The fact not a single person was able to give him comfort at his lowest, or the reassurance he wasn't weak or useless, it's pretty sad. Not Maria (she actually did the opposite) and not Ji-eun because she didn't want him to change. So in the end he felt alone and hopeless, which ultimately drove him into despair.
Since then, it seems Ji-tae is fighting with the mindset of accepting death as the punishment for losing (Just as Maria told him when she berated him). And guess what? When he was fighting Young-woong in the sewer, he acknowledged that if he let go of the armbar he would die. What happened? He let go and lost consciousness so, in his mind, he couldn't do it alone, was useless once again, and should have died. But Maria saved him.
TLDR: The guy is pretty much suicidal right now.
