Veil of Mist Warp
Explanation
By doing a very specific Powerslash you warp to the pot which contains mist, skipping getting the key to enter the treasure room. This trick has been patched in the 2017 remasters.
How it works (NG+)
The rope for the pot can be cut from any distance. This was probably done because the distance from the rope was too large so they changed it so the pot was loaded from the very beginning, rather than when you get close. So by angling your camera to a very specific angle and powerslashing in the right spot you cut down the pot. Since cutting the pot triggers a cutscene where the camera is focused on Issun so Ammy is repositioned. So it warps you down at the pot.
NG version
Currently not in use because of cutscene skips and other optimisations. By first going up at the feet to where the key is and grabbing it. That gives you a consistent spot to angle your camera for the trick. Video: https://youtu.be/dqdOiPUwM3A
Tutorial
Tutorial for NG+ AB in both 16:9 and 4:3: https://www.speedrun.com/okami/guide/g6ch9
Credits
First discovered by Kwanzai in February 2015 Rediscovered by raku on 25 December 2015 Final setups made by Kyzirado and Kinnin11 at the end of February 2016