I'm amazed by the complexity of your game. Enemy AI, amount of weapons and items, character movement options and different attacks, you even have voice acting! I accidentally killed one woman and one of the targets found her, kneeled down and apologized her he couldn't save her.
I like the level, I'd say it has a natural flow - front heavily guarded, possibility to sneak from the back, first target can be killed pretty easily once you know where pathfinding's gonna lead him. Sumo dude can be killed stealthly pretty easily too (but entering the water should alarm him I guess?). Ninja target surprised me, I attacked him from stealth (invisibility charm) and he managed to execute ninjutsu with a piece of wood anyway? It's kinda fun but maybe giving a different feedback after attacking him would be better. I felt like I had to kill him twice.
Another great plus is interactivity. Breaking windows, destroying vases, items that can be found in different rooms. They could use of furniture though, plenty of rooms are empty.
Now for the balance - I abused front roll as that's the fastest and stealthiest way to traverse level. I think it kinda breaks the game, but then again running on the wooden panels sounds pretty loud and enemies definitely can hear it. Walking crouched though is pretty slow. It's a trope in stealth games that crouched = silent, but I'd expect that a thin woman trained in the ninja ways can move silently while walking or running.
Pathfinding could also use some work. I had enemies stuck on their way wiggling awkwardly, probably when moving from ground to wooden floor. Their return to relaxed state after finding assassinated colleague also isn't natural. Maybe they could alert their friends? Maybe they even do that in certain circumstances but that never happened to me. They do alert them when they see me though.
What your game really needs is UI or any HUD interface. I very much like 3D models, environments and the like but having just simple descriptions for picking up items in default font kinda disappoints. When everything looks that good but there's no eyecandy for your health, items or just better font then it just sticks out.
I can jump and do a sommersault but I can't attack with a katana when doing that? You have to do it. It's the pinnacle of extra juice.
I had enemy below me once but there was no instakill and jumping down with weapon executed frontkick too.
I went to the level emptyhanded and even though it wan't a big deal I find it strange that you would go for an assassination mission without any equipment. It could be added as an achievement of some sorts and I believe that the game can be adjusted to have multiple different objectives on the same levels (like in MGS V) so you could expand the game significantly without the need to be in the level mines creating content too much.
Also first time I used my laptop to play it and every 5 seconds or so I had a freeze, like some big chunk of logic had to be calculated. It didn't happen on my PC but it's on the highher end so...
Also I felt down through the level once. I went into the river and then bye bye level, BUT it was at the time I found the debug options for increasing the speed of your character, so maybe I just was moving too fast and collision didn't catch me in time.
Long story short - I love it, it's pure joy to play and with a little bit of polish it's gonna be a true gem.