It seemed like some cheesy bullshit that'd require save states to get enough trial-and-error in to find the solution, so I tried it myself. It's hilarious the number of hits required to kill them goes -1 every time you die.
I found a series of inputs that seems to work every time they're performed almost perfectly. 8 HP statues, no autofire, tons of wearing out my controller's buttons.
... fuck, instead of writing out a guide by itself I'll include an AVI first...
... okay it's 10,000 MB per second for AVI, so I have a 21.4 MB mng file instead. Whatever the hell that is. I'm really hungry, but I'll try to figure out how to convert this bullshit...
...so hungry...
... alright that took less than half an hour, I was expecting it to take so much longer. I'll write the guide while it's extracting....
Something that's very important to keep in mind when coming up with any strategy here, the #1 priority is to hit the higher statues as much as possible. The ones on the ground will die long before the others do, the only statue that matters is the last one. Minimizing downtime is essential - if you start the stage by firing while on the ground you've maybe already lost. You neither move right nor jump in the air while you do that.
The Approach
Hold right until your guy starts moving, then immediately jump to the right and hit the middle and bottom statue. Pause briefly, and hit the middle statue again. PERFORM THE NINPO IMMEDIATELY AFTER THIS HIT LANDS WHILE STILL IN THE AIR. Be a couple steps away from the frontmost statue,
it can hit more times the closer enemies are to you. (At least the ones you
can hit, as the ones in the fourth row way above the top of the screen require the full eight hits to kill). The optimal position for safety to be about your character's width away or slightly closer from the frontmost statue. Then retreat to the left.
This is a rough estimate of the sphere where the statues will take 4 damage from the bomb.
The Retreat
Move left for a bit, then right a little.
Getting bumped wastes time. But so does moving left! And moving too far left will have a little bit of downtime where the second row of statues aren't spinning, due to the added travel time to your shurikens. I get the most consistent results by having the right side of the _HA sign lined up between the sword hilt and your ear.
MASH
Mash the shoot and jump buttons together. MASH THE SHIT OUT OF THAT FUCK.
There's really only one thing else you might do during this phase, and that's if you undershot your positioning, you can move yourself forward a little bit while in the air to correct it. If you overshot your position, well... hope things will work out, somehow? Also note you can correct your position if you get bumped too far back from the first bump. You can survive one more bump if the left side of the _HA sign is between your sword and ear. Moving forward is crucial to save some attempts.
You should get bumped once during this phase.
The Final Statue
A little tricky, but you have to stop mashing the jump button when the last statue hits the ground. Or your shuriken might fly over his head, which wastes precious microseconds. (Getting bumped while in the air also knocks you back further.)
The final bump should happen here. Your balls should be nearly on top of the electricity thanks to your superb positioning skills. It's important to resist the urge to press down and crouch, that will make your hitbox bigger and maybe kill you.
... so does shooting while standing.... and jumping.... all these things make your hitbox wider as well. Maybe not as wide as ducking. I'll need more research to know for sure...
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And now the file's done cooking. ... a 500 MB Avi file. For thirty seconds of button mashing. There really feels like there should be a vastly more efficient way to turn 18.4 MB of beautiful PNG files into an absolutely horrific, greasy awful AVI file...
Here's the greasefire. Youtube processing somehow made it even worse.
... But yeah, without Ninpo it's impossible without exploits. There isn't remotely close to enough time.