The bloodshade katana's definitely your best bet for stealth builds and you can grab it pretty early in osaka. When you reach the burnt village of nakajima, look west for this massive castle-boat sitting in the water - that's your target. The guards follow a strict patrol pattern, waiting exactly 45 seconds at each post before moving clockwise, so time your approach when the deck guard reaches the bow. Swim up to the western hull where there's this broken section of railing, perfect for climbing without being spotted.

Once you're up, stay in the shadows along the starboard side and watch for the two guards that cross paths every 30 seconds near the cabin entrance. The legendary chest is through a breakable window on the top deck, but here's something interesting - if you time it right you can actually chain-assassinate both guards during their patrol intersection, giving you a clean 12-second window to grab the katana.

The real magic happens when you start using it though. The katana applies an 18% bleed buildup with each hit, and thanks to its special engraving, that bleed effect won't decay over time. When you're setting up assassinations, try positioning behind support beams or doorways - enemies take exactly 2.5 seconds to turn around after reaching patrol points, giving you perfect windows to apply bleeds. Pair it with critical hit gear and focus on striking exposed areas between armor plates, since that'll boost your affliction applications by another 25%.