Honorable mention: Leno. As mentioned by many people previously, in another series, he would be the typical main char. Regardless, he is a true bro and I hope he gets a numbered kaiju weapon in the future alongside Kikoru.
3. Hoshina = I must admit he grew on me. I didn't care about him during the test, but once Kafka joined his division, his interaction with Kafka and his overall character depth made him my favorite of the 90%+ fighters so far. On top of it, this mf sure knows how to rumble.
2. Kikoru = A twin-tail tsundere is one of the most overused tropes in Anime history, so again, I expected cliches after cliches for her. But then she declared that no comrade of hers was gonna die on her watch and she layed the smacketh down on the test kaijus (before K9 intervened). She then showed another worth by keeping Kafka's secret and proved that she is progressing nicely as an ace for her division instead of being the lovelorn damsel in distress. She is loyal as heck, too, as proven with the whole Isao testing Kafka drama. Also, the dynamic between her and Kafka is much cooler to watch than Mina and Kafka. Definitely best girl of the series so far.
1. Kafka = Well, duh. Not only he is more relatable to me than most Shonen MCs (probably because of our age, previous dissatisfaction in life, and a second chance at proving ourselves), this guy is also just so engaging to watch. He is naturally funny, loyal, and capable of showing courage and conviction when need be. And unlike a certain pirate jesus, his mistakes were costly and he had to, at every turn, prove himself not only to others, but especially to his own soul and humanity (aka he can't afford to be reckless). This manga is unique, especially, because its MC was not allowed (and will not be allowed) to be in a comfort zone for too long before shit drops. Maybe that's why his ability as K8 resembles how he need to constantly adapt to the change in his surroundings? To top it all off, this guy knows how to take names and kick ass. Whenever he fully transforms into K8, we board the hype train and an epic ass-kicking follows. Lastly, he has solid chemistry with every other protagonist and is overall someone you just want to cheer.