I'm going to try and not bring up the flavor of the module, and things I disagree with setting-wise. This is just about the module and my experience with the game's mechanics.
[spoiler warning]
The module is bad. Real bad. The adventure begins with a murder mystery where you're intended to find zero evidence. There is no evidence to find. Everything you need to know is told to you by the introduction, head south to the wall.
On top of the investigation being unsatisfying for my group, as there was no potential to succeed in any capacity, the process of investigation was a nightmare. After being told there were TN bonuses and penalties based on your approach, my group spent nearly 30 minutes discussing 3 different rolls to try and figure out what the best approach would be. They guessed wrong on all three, and as a GM, the three "proper" approaches didn't make any sense at all. It felt random. Overall I think the TN bonus/penalty system based on your approach is a huge mistake. It creates a ton of stuff to memorize (25 individual approaches) and it also makes every check a puzzle (you're encouraging this slow play pattern by rewarding players for taking their time to think about it).
The dice. The dice. They're just so awful. Making a roll is like wearing a straight jacket. At keep 3 (which unless the players invest 12 XP out of their starting pool, that's their cap), you can't do anything exciting at all. Unless you explode, 2 successes and 1 opportunity is all you can achieve. Even if you do explode you're still looking at 2.5 successes and 1.5 opportunity, generally speaking. There are the cases too where you get 2 opportunities on your initial roll, so you have to make a choice. Guarantee to 2 opportunities and gamble rolling a success on the explosion, or keeping 2 successes and gambling on the opportunities. Players can agonize over these choices and it slows things way down. The dice are easily the worst part about playing the game. The more my group got through he module the less they even wanted to roll dice, even for tasks they were good at.
Combat might be fun if it wasn't so swingy. I ran a few packs of enemies (from goblins up to lost samurai) and all of them were incredibly easy for my party (24 XP as recommended by the module). Meanwhile the oni boss at the end killed two party members in a single round and didn't even roll terribly well. Further, the fire, air, and earth stances are all incredibly broken in their own unique ways, while water and void seem pointless to me. In combat especially, attacking as fire can add 3 success to your rolls with little downside, as crits are so exceedingly rare and damage is relatively low (a lost samurai averaging around 2 damage a hit unless I chose to go into fire stance). The earth stance making you immune to activated critical hits is janky at best on players, but incredibly frustrating for NPCs, and air stance is so powerful because a +1 TN to be hit when everyone's keeping only 3 makes you nearly untouchable. Dueling is neat in concept but in practice the optimal play seems to be to only center and you alternate between your stats to keep yourself calm and enrage your opponent. Being at TN 4+ to hit is basically invincible at this level range.
I don't think I need to even say that the Crab are written poorly. They send you out on MMO style fetch quests, refusing to send advice to their boss unless the emerald magistrates do busy work for them. I mean, a Hida Officer refusing to give battle advice to their commander unless the players find some drunk Crab in the stables? (This isn't to mention that the advice they give is terrible. Keeping the gates closed makes the mass combat a guaranteed win).
The Mass combat legitimately took me hours to even grasp. There's some serious editing problems. How many of each cohort type are available? What is the terrain of the mass combat at the end? How many "hida wall" fortifications should there actually be? Why do they give 10 reduction? How are the shadowlands forces intended to hurt anyone? Why don't stances apply in mass combat? What happens with strife in mass combat and does it or does it not interact with panic? If movement isn't a thing in mass combat, how exactly do you determine when it is required to abandon a fortification to assault or rally a unit? When the GM says so? Again. I like the concept but the execution is awful.
Overall the only fun I had running this for four hours was making fun of how obtuse the rules were with my group, who grew to resent the system rather quickly, as they were repeatedly failing even TN 2 tasks with regularity.
It is easily one of the worst systems I have ever played, and a lot is going to have to change for me to consider playing it again.