Felix turns his head towards the girl. She finally said something. Great. He doesn’t trust it.
Felix debates in his head if he should respond.
On one hand, it’s rude not to answer when someone speaks to you.
On another, other hand, he doesn’t like this person very much.
Also, he's rather good at hiding is nervousness. If he wasn't, this would have been a very different encounter.
On his non-existent third hand, he was just into an awesome idea for a prank, and doesn’t want to forget it, though he doesn’t know what kinds of punishments they have at Hogwarts.
And on the imaginary fourth hand, he was working up the courage to ask the sketch girl what she’s drawing. His brain is thinking through all the possible outcomes of answering, Felix’s extremely pessimistic side finding more results than the optimistic part, and, after deciding that he will, in fact, respond, he’s left with the next question: what to say. He almost defects back to ‘say nothing and ignore her’ but tries not to. Felix does that far too often. Also, managing to keep his tone even will be a struggle. He’s still pissed at ths girl, and she’s hardly racking up any points right now. He’s been quiet for too long, she’s looking at him funny. “Okay?” he says quickly.

Kaia is entirely unimpressed by the sequence of events that has transpired. She still doesn’t like this upstart of a girl, even if she did apologize. On the other hand, the boy seemed like an interesting character, in a more positive way than the girl. She goes back to her dragon, keeping half an eye on the other two, just in case something funny happens. A primal instinct inside her makes her want to defend this boy; she likes the looks of him. He seems like he could be a good person to hang around with, if maybe a bit quiet. He was weird, but not in a bad way. In a way that Kaia liked. She never used the word “weird” as an insult or derogatory term. Actually, she used it as the primary way to describe herself most of the time.
By the time the girl speaks again, Kaia has finally managed to get that curve in the dragon’s neck right and has started on the outline of the skull. At the sound of another person’s voice, she pauses, looking up at the speaker. “No idea,” she replies roughly, expression blank. Another moment of silence in which Kaia just stares at the other girl, then she sits up again, putting her sketchbook down beside her with the drawing facing up. Her hand goes forward, towards the boy, very pointedly not giving any sense of friendliness to the girl, for him to shake. “If we’re going to be here much longer, I bloody well suppose I can’t sit here the whole time ignoring you. I’m Kaia.” She waits for him to shake her hand and respond, with a posture and expression that’s not quite happy, but somehow manages to express that she is interested in getting to know him.

Felix reaches out to shake the girl’s hand, accidentally putting out his left hand, by force of habit from Scouts, but corrects himself. Felix shakes her hand, saying “I’m Felici-er, Felix. Nice to meet you, Kaia.”. She seems nice enough, certainly better than the other girl, and he’d like to talk to her more. Kaia seems cool. Her hair is pretty awesome, dyed blue and red.
Maybe they’ll be in the same house at school. It would be great to know someone there.
Also, this is probably his best chance at making a friend at this school. He already knows that it’s a good idea to have at least one friend in a school setting. He doesn’t mind being by himself, but at school, he’s learned that being solitary can cause problems for you.
He’s still annoyed with the other girl, and honestly has no wish to speak to her. He avoids showing anything but hostility or indifference towards the second girl.
Felix takes a breath before asking “What’re you drawing?”. He doesn’t lean over to look, because people do that a lot to him and he hates it, so he just waits for Kaia to answer.
He hopes he doesn’t come across as nosy. Lots of people say that he is, and most get mad at him for it. He likes Kaia so far, and doesn’t want her to dislike him.

Felix takes the offered sketchbook. Kaia is getting even more interesting by the minute. He flips through a few pages. He likes the dragons the most. Though, to be fair to the hippogriffs, Felix likes almost anything with dragons the most, but these drawings were his favourite so far. Makes sense that Kaia was so absorbed in her sketch pad before. You kind of needed to be to do things like this. And definitely invested in it to colour them in. She pretty obviously loves sketching, if she focuses on things she likes, like most people tend to do.
When he used to draw a lot, he never coloured anything, and only sometimes shaded. And he never felt confident showing them to anyone.
It’s clear that Kaia spends a lot of time on each sketch. “These are really good.” he says, looking back up at her before resuming his flip-though.
There’s one hippogriff that catches his eye immediately, and then he voices the question that he first wanted to ask when he started looking at the sketches. “You like hippogriffs a lot? I mean, I’m just guessing, but the majority of these are hippogriffs, so I assume you either like them or you like sketching them.”

Felix looks at the drawing Kaia had handed back to him. The highlights shine in the sunlight through the window. The golden eyes of the hippogriff kind of remind him of his chicken Mayday (he stopped telling people her name after many kids asked why on earth he would name a chicken ‘mayday’), back home.
He wonders what it’s like to grow up with a wizarding family. He doesn’t think that his dad, Amandus, counts, because it’s not like he ever uses magic or talks about it or anything. “Awsome! Caligo seems like an interesting guy- or, I guess, hippogriff, but either way.” he mentally scolds himself for tripping up so much on his sentence, but soon gets over it. He suddenly remembers the other girl in the compartment, still sitting with her book on the other end of the seat. She’s clearly not reading, or at least, not reading at an average human speed, which Felix can tell by the fact that she hasn’t flipped a page in absolute ages, but if she’s leaving them alone, he supposes that fake reading is okay.
Then he thinks of something “Your family’s all magical?” he asks Kaia, unsure of how it will be received but too curious to care.