@WillLi Not sure how can you say we don't know what's going on with Jitae when the series has even relied on narration to explain that Jitae's is "acting tough" in order to avoid being perceived as weak, which is how he actually views himself.
Jitae isn't a normal kid, he's dealing with some serious trauma when it comes to his father. Not only because he assaulted him and left him with a physical scar, but because he was powerless to do anything about it, and his sister was taken away from him as a result.
All the issues he's been avoiding in regards to that situation have been brought back to his life since joining the Fight Classes and teaming up with Maria. And to make matters worse, each of his shortcomings are a big blow to his already shattered ego. The more he loses, the more he believes he's "useless". The more he fails, the more he hates himself for being weak.
This "personality change" we're witnessing is more of a coping/defense mechanism than anything else. He's realized that the way he is, and the world he's stepped foot into are incompatible. So he projects a fake persona more fitting of the cruel reality he's decided to embrace in order to get back his sister. And to do so, he fuels on his rage against himself.
It is jarring? Damn right it is! I think Jitae's current behavior is supposed to make us feel uncomfortable. I don't think we're supposed to feel good about how he's acting or enjoy how "extra" he's being right now. But as a character progression, is really interesting to witness, and I can't wait to see how the author is gonna resolve it before the beginning of the 2nd semester.
@ReyKaNeel It seems the people living in The Tunnel view themselves as social rejects or pariah. That's why Bob Sopp said: "I don't belong here".