In 2009 I was watching Youtube speedruns of the Nikujin training level. I came across one that did a trick that I think the author called a "high jump" (unfortunately I can't find the video anymore). The author didn't explain how it was performed, and also didn't use it to do anything interesting, but I soon figured it out independently. A while later, I realised it could be used in a couple places on the training level to save a bit of time.

Now, in 2011, after remembering someone posted a Nikujin run on SDA, I found myself planning routes for the 10 levels. I did this all before actually watching Daiz's SDA run, but I had only a couple changes to make after seeing it. My route planning was very thorough, I spent a lot of time going through the game and finding more glitches and tricks than I ever thought possible. I was happy to realise that this run shows off all of the ninja's moves and almost all of his glitches and tricks. When they piled up I realised there was no way I could pull them all off in a single segment.

I figured out that as long as I restarted the game before dying or finishing a level, the game wouldn't be able to save that it happened. The problem was that I had no idea where Nikujin saved its data, so once each level was completed there was no going back. It's a really stressful way to play a game... not restarting in time means scrapping the whole run. I had a couple of panicked moments... but let's just say I was just extremely relieved when the timer at the end said 2:12.

Below are the techniques that appear throughout the entire run. After that is a breakdown of each of the 10 levels. The run is segmented per level so each level corresponds to a segment. Before I start, though, I'd like to take a quick moment to thank all of the SDA staff and everyone who helped with the run. So... thanks... I really appreciate it.

The most important glitch of all. As ExplodingCabbage noted, there are three different jump heights. The first is the normal jump which lets you grab ceilings 3 blocks above the ground. The second is another half block higher, performed in a variety of ways (which I won't explain here because it's only used once in the run... it's only really useful in a TAS). The final is the actual high jump, which lets you grab ceilings 4 blocks above you, breaking many levels. Perform it by pressing left, right and jump together, with at least one of left and right being pressed simultaneously with jump (failing the timing means getting the 3.5 or 3 block jump instead). In the first frame of the jump a lot of height is gained, so it is easily distinguishable from a normal jump. It can be (and, throughout the run, is) performed while moving, but it doesn't get you much extra distance. It often slows your horizontal velocity down, so it's for heights rather than lengths. I have found it to be strangely more reliable on some of my keyboards than others, with the one I used in this run being the best.

There are two ways to turn around quickly in Nikujin, both having their own uses, and neither being glitches. The first is a simple roll, as it can be performed in either direction. It's a good choice when you're in the air. The second is done by attacking on the ground or in the air. Simply press the opposite direction and attack. This can be followed by an attack cancel for maximum usefulness.

The simplest attack cancel is jumping after attacking, and rolling after an air attack works too. Wall climbing won't cancel an attack, but the little flip at the top of a wall will. I wouldn't call any of these glitches, but the double slash (as I call it) is considered a glitch. Attack once and you'll have to wait for it to end before grabbing a wall. Attack a second time before that attack ends and you'll be able to grab it immediately.

In the last few levels I use my health wisely. You have 4 hits and a fifth kills you. Picking up health gives you an extra 5 hits, but bomb jumps will take away all 5 again. Besides this, hits from enemies and falls do 1 damage, and spikes do 2. Where I need to boost off a wall after falling, I always take the damage instead of rolling to avoid it.

A couple more glitches only useful in this level are shown off here. The first is the music glitch. When you disable music, the loading of the level messes up. Among other things, your movement is disabled for a moment longer. I use this to be able to hold left as the level starts and not die. I do a double slash to boost quickly off the hidden crate in this level; a technique I use in just about every level. I break the gate with pixel perfect timing (the only actual pixel perfect thing in the whole run) so that I'm in the right position to do the next glitch. The height that the first frame of the high jump gives you is enough to get you into a block directly above you. Instead of killing you or keeping you stuck, the game pushes you downwards. If you are in the very last pixel on either side of the block (I'm on the right side), you will be pushed upwards instead of down. This is the only way that this technique is faster than the already very fast upper route as shown by Daiz. Continuing to hold left and right and jumping is one way of doing the 3.5 block high jump, so I do that the rest of the way up. The last bit of precision I need is at the top where I have to stop and boost away quickly... so this segment turned out very well.

I enable music again between segments, and keep it on for the rest of the run. This level has a few high jumps for height gaining, and a combined boost/high jump after hitting the button.

This one is the same as Daiz's route, but I do a high jump to get straight up on top of the level. The two jumps at the end of the level actually aren't pixel perfect, despite what Daiz said, but they're pretty close to it.

I high jump right away to get up to the first ledge. Due to some unavoidable weird glitch, probably the same glitch that takes away Daiz's run-speed in his run, I get thrown an abnormal way to the right when I flip up. After this I do a few more high jumps, and the best spike hugging I've ever done on the way down on the far right side. I credit Daiz for the roll off the far side of the final pit, which gets me to the end quickly.

As this level starts, I'm tapping jump rapidly to do a small hop, and after that I roll. This gets me the perfect extra distance to the right of the level, enough to see half of me on the left of the screen. Any further, and you are teleported back to where you would normally start. The rest of the level is normal: a quick neckstab, and timing a jump to hit the arrow as it appears.

Here, and for the next three levels after this, I use all of my 4 hits. I take my first hit on the fall at the start to boost immediately. The jump I do there ensures that the purple guy will miss me. I have to manipulate luck to get the bomber facing away from me. For a variety of reasons, the chance of him seeing you is noticeably higher than the chance of him not. Once I've gone past him and let him see me, I do a quick turn with an attack and jump, and then a quick turn back with a roll. All of this means that he runs and breaks the wall, and I get in ASAP. This is much faster than waiting after killing him, as Daiz had to do. I take my second hit on the fall from the button, and keep my last 2 for the purple guys on the next platform up, who promptly take it.

I take a hit on the opening fall. On the high-jump-abused climb up I can't take a single hit from any shurikens. My second hit again goes to fall damage. I do a big flip up to where the bomber is, to delay him seeing me, which paid off. The quick turning here is pretty poor... the ugliest mistake in the run. At the top of the spike shaft I use a flip to cancel the attack breaking the gate, then continue holding jump to do the next part. Rolling on the spikes while holding jump causes you to bounce higher than you normally would, and it's just enough to get me to the end. The 2 hits from the spikes here are the last of my 4.

After the disappointment of how the previous level turned out, this one went better than I ever imagined; being the most technically difficult of all the levels. I start the level holding right, and boost immediately. My double hop technique here usually lets me avoid all shurikens. I have 2 miscellaneous hits to spare, but I'd restart if I was hit here. A high jump and a nicely timed wall jump gets me to the next purple guy. Here you can lose health in three different ways. The purple guy can hit you on the way down to the button; you can take fall damage if you don't do a short enough hop; and you can be hit by the purple guy when coming back up and running away. All of this has to, and did, add up to a maximum of 2 hits. A boost immediately followed by a high jump gets me to the button and also into a position to get straight back up. The bomb jump next is pretty crazy. I need him to see me, then jump, but still come into contact with him so that he explodes... and slow the run down enough to make it to the right. The spike hugging I do here is probably the best I did in any attempt. The spike bounce next works the same way as the last level, taking away my last 2 hits. The green guy in the pit is polite enough to kill you if you don't make it there fast enough. I complete the level in a fury of blades, which turned out very well despite having no health to spare. It's actually harder than it looks. A lot of attempts were trashed right at the end because of it.

The high jump had its largest impact here, reducing this level to being one of the easiest. I move to jump straight off the edge of the first platform, trying to get as far as possible. Rolling works normally on the spikes at the bottom on this level, for some reason, but you still lose two health each time you hit them. I roll, jump before it ends, roll, and continue it into a neckstab. That's all 4 hits gone. The high jump to the next platform is very precise: you often won't be far enough along the bottom of it to flip up. The bomb jump at the end is the only other thing taken from Daiz's run. The bomber needs to be facing towards you.

As in Daiz's run, all of the kills are neckstabs using the bosses' weaknesses. I start the level holding jump to be placed further to the right when the battle starts. For the first two bosses, I move to the correct places and cancel some well-timed attacks with short hops continuing into neck stabs. For the final boss, I move to the edge of the platform and jump so I'm at its peak when he's under me. If he's any closer, he'll grab and kill you. I then complete the level by grabbing the arrow as with the other boss... and celebrate!

Back in 2007, I recorded the first no deaths speedrun of Nikujin ever.[1] However, it included quite a lot of mistakes and time-wasters, and was subsequently beaten by other people playing the game.

Now, in 2010, I'm back with new speedrunning techniques to make for what is pretty much the ultimate Nikujin speedrun. I made a few small mistakes here and there, but other than those the only real way to improve would be with additional luck, since the enemy behavior is highly random.

A breakdown of the techniques used in the levels:

Level 1: Ninja Fortress 1
After breaking the gate, taking the upper route is considerably faster than the lower route.

Level 2: Ninja Fortress 2
This is mainly just smooth movements. The one thing to note is the first drop to the red button: You need to slow down slightly in order to be able to boost instantly from the right wall.

Level 3: Ninja Fortress 3
Includes one of the biggest time-savers by skipping a large portion of the level completely via two pixel-perfect jumps on the right platforms that would be crossed during a dash under normal conditions.

Level 4: Inside 1
I make a small jump at the beginning as a pre-emptive measure against a bug that kills your dash speed after your first jump in this. However, it still happened, which slowed me down a bit. At the top level, I pull off another pixel-perfect jump to cross the spikes so that I don't have to stop and turn around for a dash from the left boxes.

Level 5: First boss
The boss is vulnerable to one-hit kill during the pause after he attacks with his both swords. To make him do the two-sword strike, you just need to run towards him and continue running past him.

Level 6: Dungeon 1
Nothing really special here, though I realized while watching the recording that I could've probably saved a few moments in the end by dashing from the top-level boxes instead of just running and jumping normally.

Level 7: Dungeon 2
I came up with a new technique for this level on one of the record attempts. This technique is the dash from the right wall at the start of the level. Do note that while it saves time, it's also a gamble: There's no guarantee that the purple enemy is looking left at the moment you get there. This ruined quite a few record attempts for me.
In this level I also made what is probably the biggest mistake in the entire recording, aka falling from the spike shaft in the end. This is one annoying spike shaft. There was also the waiting time earlier on the top level, where I had to stop for a while to wait for the guard to turn around so that I could neckstab him (only guards that aren't aware of your presence can be neckstabbed).

Level 8: Red Dungeon 1
This level has one of my favorite techniques right in the beginning: By being extremely fast, you can get directly up to the second level and jump over the green enemy just before he turns around. A slower player would have to hang underneath the bottom-left edge and wait until the green enemy walks all the way to the edge and turns around, and then wait some more until it gets to the appropriate position for a neckstab-jump.
When I go press the red button, it is crucial to kill the purple enemy: He can quickly chip away your health to lower than 5 after getting the life potion, which will make the upcoming bomb jump impossible.
After killing the purple guy on level 3, I use one of the green enemies down in the red button room to get to the button as intended, but instead of the intended way of waiting for the another green enemy to walk to an appropriate position for another neckstab-jump back, I simply drop down and use the left wall to get up.
On the top level where you have to kill the four green enemies in order to progress, I simply get detected by all of them and hide behind the box: After this, I can kill them all with a single neckstab. For the game's kill counter, this only counts as a single kill.

Level 9: Red Dungeon 2
No real time-saving techniques used in this level, just some luck in enemy behavior and good timing.

Level 10: Final bosses
First boss single-hit KO: Keep a distance so he does the staff throw. Hit his staff. Neckstab him while he's dragging his staff back.
Second boss single-hit KO: Keep a distance so that he will throw a... bullet. Hit the bullet so that it reflects back to the boss, and neckstab him while he's recovering from the hit.
Third boss single-hit KO: Stand on a ledge so that the boss does his dash move, jump out of his way to the wall on the left, walljump off and neckstab the boss while he's trying to keep his balance on the ledge. Stay away from him when he's dying, since he's going to explode before he's fully dead.

References:
[1] http://www.youtube.com/watch?v=Fo6p40RpzrU