Guide to beating every level as fast/reliable as possible

Hold right + jump the entire time
Hold right than press jump a bit later
Hold right + jump at the start and on the moving platform, continue to hold jump, try to land on the left side of the first platform whilst going left, jump left. Try to land at the rightmost side of the second platform whilst also going right and hold right + jump.
Hold right + jump, than right or Hold right and then jump and then just right.
Hold right + jump, than just right
Hold left, hold jump when you pickup the second star, as early as possible, and keep holding left for a bit. Try to position yourself on the leftmost part of the platform/one bit righter, so when you hold right + jump you won't bonk, on the leftmost side you also won't pick up the ninja star. Throw the ninja stars away with space if you feel like it.
right, jump, space, left, space, jump, right + jump, right, space, left + jump + space, left + space, right + space.
Hold right, jump once, throw the shuriken when you can hit the ninja, sometimes you'll die, which is as far as I know just luck, but there might be a jump timing which minimizes this.
1: Hold left, jump right before where the first ninja stands when the level starts, hold right and sometimes jump to weave through the enemies/shurikens 2: Hold right, then left, jump at the same place, throw the shuriken when landing on the ground and go right, sometimes there will still be enemies, so try not to die.
Hold right, jump once, you can jump exactly over the 'shrine' but this has a high chance of you bonking and doesn't do much.
Hold right, hold jump a bit after going underneath of the platform with the ninja, you shouldn't bonk on the stairs.
Hold right, jump right before where the ninja stands when entering the level, close to the edge of the platform
underneath. Switch to your katana if you haven't already. Hold left after clearing the first platform in the air, continue to hold left. Use your sword to reflect the shurikens and jump over the (now dead hopefully) ninja so you fall faster. Hold right in the air after clearing the second platform. Jump when landing to dodge the spears, occasionally you'll have to reflect them. Murder the spear guy with your katana when landing because he's annoying and equip the shurikens before entering the next level.
Hold right, press space when you get the shuriken and hold left. If you accidentally throw it to the left, throw the second shuriken to the right, this will only lose half a second or so. Press space when you get the second shuriken and press right, you can wait a bit with this so you won't accidentally throw it to the right. Jump a bit late so you don't bonk on the dissapearing platform, hold right and murder the spear guy with your katana. You can jump on the ground to be sure he won't kill you.
Hold right, jump at the edge of the platform. Equip the katana if you haven't already.
Hold right and up to get into the first 'hole'. Tap up repeatedly a bit beyond the beginning of it so the shuriken guy will attack straight ahead. When the spear guy attacks, swim up and reflect the spear. Go to the right and reflect the shuriken. Go to the left and down, jump on the ground (you can jump underwater) continue to hold up, grab the shuriken and switch to it, then throw it to the upper guy and hold right to finish the level.
Either spampress space or try to time it to get through the dialogue. You can attack with your katana during the loading screen. This doesn't do anything, but is something to do. Hold right + jump at the start of the level, throw a shuriken when falling from the second platform to murder the second ninja. Throw an extra one to be safe when jumping from the ground. Continue to hold right, and jump when your second shuriken hits the ninja/where the ninja was. Hold right and deflect the spears. Jump after passing where the underground hole stops, continue to hold jump and press left a bit after jumping again so you won't bonk. Hold right, hold up to go up in the water and murder the spear guy from underneath. Jump up from the water and hold right, throw the shurikens when you get them and jump when you reach the overhang. continue to jump to the land. Jump when the overhang goes offscreen so you'll fall faster down the hole. Press jump a bit after landing so you won't bonk and press left and right +jump to platform up. You might accidentally doublejump when grazing the second overhang, you can use this to fall down faster by instantly pressing right after it happens. Press right + left + right to fall down and jump right after landing to doublejump over the stairs.
Hold right + jump, you can jump a bit after holding right to not bonk on the wooden beams, but this doesn't do anything special.
Hold right + jump, switch to the nunchucks and press space whilst holding right. You can jump early to fall slightly faster, but this is hard to time, and might make you die from the shuriken, unless you always time a perfect katanaswing.
Hold left, jump after collecting the second shuriken, hold right when falling and use the nunchucks to not die. jump clear the level, if timed correctly, you won't bonk.
Hold left, you can either go down and jump underwater to go around the obstacle or go up immediately and use your katana to kill a couple of piranha fish. Land on the obstacle and use your nunchucks to kill the piranha's infront of you, you can move around/use your katana to improve your odds of surviving. Jump to grab the shuriken and go back. You can either go down to the bottom platform whilst throwing the shuriken and then go up, or go down untill you're at the level of the target, throw the shuriken and go up. The last one is probably a bit faster. Whilst swimming to the end you can jump out of the water to move a bit faster, but this might make you boink.
Hold right, jump, move on the platform and jump again. You can throw a bomb and reflect it with your nunchucks if you don't want to die from boredom. You have to switch to your nunchucks either way.
Hold right, throw the bomb as soon as you have it and stop. Spin your nunchucks and move right again so the bomb reflects to the target. Jump after deflecting the bomb so you fall faster. You can use the second bomb to try again or just throw it away. Switch to your katana.
Hold left, kill the first guy with your katana if you want to and try to time your katana strike to deflect any potential shurikens from the second guy. Go right after clearing the last skyborne platforme. You can jump and kill the second guy after that if you feel like it. Switch to your nunchucks.
Hold left, spin your nunchucks and go down if you are sure you won't die from the first/second piranha fish from the left/to not die from the third piranha fish. Switch to your shurikens.
Go right and left unto the small platform underwater. Jump off it and collect the shuriken. You can move to the right/left to boink on the small hooks under the top platform and go down faster. Go left and break the target block, go into the hole and move to the right and prepress up.
Hold right and up, switch to your shuriken.
Jump to the right and after landing, move to the left and throw your bomb at the edge of the platform. Go to the right and jump.
Go to the left and press down. Fire a shuriken at the piranha fish and move around the obstacles. Safety is more important here than time. Kill the piranha('s) with your katana whilst going up.
Hold right, jump at/slighly before the bamboo and kill the two snakes a bit before landing in the hole. Buffer jump and stop holding right/start holding left as soon as possible to leave the hole. Go to the right midjump.
Hold right+jump. You can kill the first snake with your katana to make sure it doesn't kill you, but this rarely happens. You can throw a bomb during the first jump to kill the second piranha. Switch to your shuriken.