The thing that ruins it is that the creators left pretty much nothing for the characters or plot. The show clearly is trying to do too many things and it really needed to cut some of the content off so everything was more cohesive. If they cut the kid, the show could be more focused on the crime drama and action. Cut some of the crime and drama instead, and we get a more interesting found family adventure. As it is, the show is very distracted and constantly feels like each part is trying to push the others out of the way.
A major failing of the show is that the main pair never really develop. From the description, it's clear that they are going to have a rough start, but over the course of the journey, the two will learn from each other and become family. We've all seen the setup about a million times before. The problem here is that the show doesn't even attempt to portray this development whatsoever, but still pretends that it has happened by the conclusion.
Actually, it's worse then that - the shows actively portrays their relationship as completely dysfunctional up until the plot requires otherwise. Even as far as the latter half of the show, Michiko completely ignores Hatchin and any of her problems, leaves her out of the loop for all of the dangerous things she might be doing, and more than once slaps her to shut her up. There's very little of the show where Michiko shows genuine concern for Hatchin, or any tender moments that would make it seems like this is anything more than a kidnapping. Hatchin has absolutely no faith in Michiko, despite Michiko's commitment to Hatchin's well-being is one of the only consistent traits she has - she will ultimately do right by Hatchin, even if it's in a way Hatchin doesn't like. Hatchin runs away at least 2 distinct times in the show and ends up joining back up with a mostly-unbothered Michiko. Once makes sense. Twice means nothing meaningfully changed.
How this relationship manages to suddenly becomes the sort of relationship where Hatchin is sobbing when they part ways requires you to imagine that a whole lot of bonding happens off screen. Just 1 episode out of 22 where Michiko takes Hatchin out for a day of fun would've made a world of difference here.
Speaking of those 22 episodes, the show would be much better if it had half the episode count. It would probably have been best if it were a movie. So many of the episodic plots are slow and just forgettable. Many members of the supporting cast are completely unnecessary and should have been cut so the ones that remained could get more screen time. The goal of finding Hatchin's dad is constantly alluded to, but is almost never developed on any given episode. It's fairly clear that each episode in the middle was written to the premise independently, rather than being carefully ordered so that there's regular progress towards the goal or towards any specific character development. When the show is nearing the end, it just suddenly points the cast in the right direction and makes sure all the pieces are where they need to be (often without explanation).
Whether you'll like this show ultimately comes down to why you're interested. If you just want a strong female lead, or you're looking for an action adventure with found family elements, you'd probably be a lot happier watching Moribito. If you're mainly here for the setting, the action/crime tags, or the staff and studio, you'll probably find some value here, but you might find that the 10 year old tends to get in the way of the action.
