Anime

There might have been an misunderstanding, the ninja squad that attack Higan's home show how with the first ninja they killed how they take advantage of openings, and how pony tail guy likes to come in after the "fodder" ninja weaken the target. That squad has been killing ninjas in that area from the news reports.

Back to Mari, she was probably disabled in a moment of weakness between killing ninja and trying to protect her child, with that the pony tail ninja( probably killed the child and threw him at Mari) waited for higan and stabbed Mari in front of him to make an opening.

I mean it did work as the "fodder" ninja was able to sneak up and stab Higan

The leader ninja forbade Zai from fighting with his old team( which Zai considered at one time family) and seems something like a retainer or right hand man( who knows the reason, besides the trope of friend turn rival showdown).

Zai seems to be blind and I am curious how that happened between present day and that betrayal. It all depends how they flesh it out, I mean sure it is tropey, but it doesn't have to have the best writing as the action scenes do a lot of the heavy lifting for the show.

Also the Auzu( who the head is obsessed with data collection - possible ninja AI learning ) acting independent and in an alliance with Ninja seems to show some friction.

There is an interesting thing I noticed with episode 5, but that is reserved for that topic I am sure.

It might be rough on the technical details but, for me, it is "logically consistent" enough that I am interested where and how the story will unfold