First impression is that this comic looks very professional. The art is very consistent and extremely detailed. Fans of manga would generally be big on this, considering the art style and black-and-white screentones. You may want to consider taking advantage of the digital format by adding splashes of color here and there (such as, making magic colored in your comic) unless you're formatting this for print.
As for the story- it cuts straight to the chase. I read up to Sion part 8, for reference, and at first I was a little confused since our main characters (Keith and Jeremy) were given no backstory or much context. They do reveal their personalities as the story goes on, which is nice, and obviously showing is much better than telling when it comes to character traits. But the beginning was fairly disorienting.
Out of curiosity, I skipped to the beginning of Sigrid to see if they'd be given any history then, but nope. The fact that a 13 year old and 11 year old are solving supernatural cases together does raise a lot of questions, though- where are their parents? Are they getting paid? How'd they get into the profession?- that readers naturally expect to be explored. I'm not sure if you're planning on giving these questions answers, but it's something to consider, especially as it would help ground their characters.
