It is unfortunatly very bland. after mc initially fights back against bullies after getting stronger he just doesn't do anything... based on his background he should be filled with anger and thoughts of revenge.. but nope. nothing. everyone who bullied him, teachers who ignored it, parents who underfed and completely ignored him, brother who despised him. nothing. no mention of his emotions/plans.
Additionally, there is no drive to grow stronger quicker by seeking out opportunities to absorb mana from people (bullies would be the prime targets, and he could do it outside of school avoiding the excuse of a teacher detecting it) or by getting his hands on beast cores. mc is content with living a normal school life and working a normal part time job to pay the rent. thus we just get normal school arc, taking classes, small duels and stuff. all this while an actual tournament arc is looming in the distance, which I cant imagine will be any better.
Bland is the best word I can think of to describe it. With that said, the premise and writing quality is good and the story is by no means irredeemable if author better explores the emotional side of the mc. Either by having him use his newfound powers to get revenge (I feel like it would be reasonable for a kid in his situation to let the power get a little bit to his head and walk down a darker path) or by clearly motivating to the reader why this isn't happening, maybe he is struggling with such feelings but is able to hold the back.
