Early Sasa Sanctuary
Explanation
By KT jumping over the loading zone returning you to Taka Pass you can perform an Interior Clip to enter Sasa Sanctuary early.
This allows you to skip the Satomi Power Orb quest and get Waterspout quickly. You can also fight Gi before getting the Canine Tracker. This makes the game think you've already fed one of the for dogs in Kusa Village allowing you to use one of them to warp closer to the village entrance.
Method
Right after entering the area, go right and jump up next to the rock. Do one KT up, using your second wall jump to go right towards the loading zone. Do one more KT to clear the loading zone and run up to the edge of the area.
Jump off, hold the map button and start aiming towards the origin mirror. When the background changes colour to a lighter blue, hold the direction for two more seconds, then let go. You should land directly in the main hall.
Example: https://youtu.be/6zAyWckl-58?t=1023
You can also land in the hallway towards the hot springs, but this is a bit more risky and should be avoided by newer runners.
Example: https://youtu.be/xQJmnMdIIww?t=991
If you land in the Sparrow Boss' room, simply jump down the elevator shaft. Make sure you don't land on top of the elevator, because this will soft lock the game.