It seems that Lee Hyun-Gul might be a mentor character of sorts for Ji-tae after this. He was probably the first person to ever try to actually talk to Ji-tae heart-to-heart, unlike Maria and Ji-eun. He also understands Ji-tae surprisingly well for the amount of time they've met, maybe because of his past experiences. While Ji-tae is still somewhat antagonistic to him, I feel that Ji-tae understands this fact and is willing to take a chance with them.
I wanna talk about the nightmare he has. It's just a straight look into his traumas and motivation. There's obviously his sister, Maria, and his self-loathing. But we also see that the life-or-death fight in the sewer haunts him, probably forcing him face-to-face with his own and other people's mortality. That's why after the sewer he starts becoming more obsessed with death, and starts beating his opponents to near-death. Also, I'm not sure if the hallway they're running through on page 29 is supposed to be somewhere specific but it might be a thing I just missed.
There's of course the foreshadowing for this chapter. Choi Young-joon (and some others probably as pointed out by @mylastchance98) came from the Tunnel, directly tying the Fight Class members back to the Tunnel. I don't think Jung-Eum will have a problem with Young-Joon's origins, but she will probably get dragged into the situation as well. There's also the deathmatch, with Chang-yee possibly being more ruthless than Ji-tae, and Ji-tae will probably have to grapple with killing someone again here.
Last note: from ch 82, Ji-tae might have gone to Steelworks for their money to heal Maria faster. Either that, or he was gonna team up originally until he saw that Hyung-Chul was part of their team, and probably lost all trust in Steelworks after that point.