@Bonticimmy As nobaka said, Ijuuin is the real (hidden) protagonist of the serie.
I honestly think the author really wanted us to show the story of a sort-of normal guy becoming proficient and growing as a person. Everyone else, at this point of the story, just want to make him grow as much as possible. He might not the the character with the most screen time, he is still green an learning, but he's certainly the main focus of the story
Proof of that is, he's by FAR the one we see monologuing the most often. We are always shown what he thinks, what he feels. Kato has that too, but to a lesser degree. We just don't see Asada's inner thoughts instead.