If youre looking for the best stealth weapon, the bloodshade katana is pretty much the way to go. I actually found it really early and it completely changed how i approached bigger enemies. You can grab it in osaka, just look for this massive castle-ship west of nakajimas burnt village - its pretty hard to miss honestly.

The thing that makes it so good, especially for naoe, is how it handles status effects. Like, when you inflict bleed on someone, it doesnt wear off over time which is super useful when youre dealing with those tanky samurai who take forever to go down. Makes it way easier to stick to the shadows and let the damage do its work.

Tip: if youre having trouble getting to it, theres actually a nice swimming route that'll get you right up to the upper deck where the chest is. Just keep an eye out for guards patrolling the edges of the ship, they can be pretty annoying if they spot you. Once you have it though, those stealth assassinations become so much smoother, especially when youre trying to take down the tougher enemies without getting into a big fight.

I particularly love how you can just apply the effect, disappear into the shadows, and know that enemy is definitely going down - its perfect for those missions where you need to stay undetected.