A teenager with like $5000 of presumably replica guns definitely isn’t a red flag.
Impressions:
Completely generic shounen, edgy flavor. The kind where the protagonist has a dark demonic power and after their father/dog/sister/guinea pig sacrifices themselves for his sake, he joins a team of radical teens, also with their own themed super powers, to fight the bad demons. The same formula as Chainsaw Man, Tokyo Ghoul, JJK, so on and so forth. And probably the same script too, though these days, I expect it to just be written by some awful AI bot.
That’s probably harsher than it deserves, considering it’s not a cheat power reincarnation story, and the animation is at least a notch above competent (not so much the direction or choreography), but it is 125% generic edgy shounen to its core, and does itself no favors when the baddie du jour stops to give a big melodramatic speech introducing himself, his reason for being here, what he’s going to do, and why he’s going to do it, like he’s interviewing for a job. All the dialogue is like that to be honest. “This may be hard to believe, but yer a demon.” “What are you saying, pops!? I’m a demon!? There’s no way!” It at least makes it through killing its Uncle Ben/Potato chainsaw dog/Whoever in the first episode, and with only a small amount of awful shounen ‘comedy’, but it’s definitely not winning any converts.