Memoirs of an Isekai in Naruto

Log 9: Vacuum Style ninjutsu and taijutsu

What is a vacuum, how can it be dangerous and how can we make it? A vacuum is a lack of anything, even the atmosphere. A great example of the dangers of a vacuum in nature is the Mantis Shrimp.

The acceleration of a shrimp claw is around 10,000 Gs and a velocity of 23 m/s. This is great enough to create a vacuum/cavitation bubble after striking its target. 

The process of everything collapsing in on this bubble creates a shockwave. This acts as a secondary attack harming its prey even if it misses. 

Another danger of using this double principle of an initial strike followed by a vacuum implosion is thermobaric weapons. I will talk about the use of fine powders and fire releases in future logs and go more in-depth on creating thermobaric bombs.

Wind release focuses on direct air pressure to cause damage like the last Jutsu I explored. Air also has a hard time dealing with large solid constructs and is weak to fire release.

Vacuum releases focus more on controlling wind to produce a shockwave. This shockwave can propagate through matter far easier leaving not just surface damage but internal damage. 

A vacuum can also snuff out the fire as it would lack the oxidizer needed for the flame. This is difficult to use on a fire Jutsu if you create this vacuum using wind release as the high-pressure wind sphere around the vacuum used to pull in the inner air could still feed a fire.

However, the instantaneous air pressure shockwave after detonation will subsequently blow out most flames.

Training 

I can think of two methods that this atmospheric manipulation might be possible. One safe for range using wind release and a second through the use of barrier or chakra compression and shape manipulation.

Ninjutsu wind release example of a Vacuum Rasengan:

One method is through the use of fast-moving air that creates a sphere and a cavity and pulls the air from both around it and inside this cavity. 

This would not only create a cavitation implosion once the sphere strikes a surface but the surrounding winds would be strong enough to cause serious lacerations or worse.

Ok, this concept is nearly identical to the "saturation subduing technique" but instead of increasing the internal pressure you will be using one's control of the wind to cycle a sphere around a point and use the movement of the wind release to create a low-pressure zone pulling the airway from the center of the sphere.

Any wind jutsu can implement this Concept by implementing steps two through four of my example Jutsu.

Step one: First like dealing with the Rasengan you will need a level of mastery over creating a sphere capable of compressing and moving chakra. Training involves using a water balloon, a rubber ball, and a regular balloon 

Step two: Second you will need to practice creating high-pressure wind fronts moving together in the same direction without losing control of the direction of the wind. Training involves getting a box putting a candle in the box and using purely the movement of air out of the box to put on the flame.

Step three: one can practice wind release natural change instead of producing the wind directly from one point in front of your hand but a sphere around your hand with a low-pressure vacuum in the center. This can be done with a candle and once you can shuff out an open flame with nothing more than pulling the air away from it you can work on sealing this vacuum.

Step four: you can control the motion of the air like that of a tornado with high and low pressure creating motion around a calm center capable of motion without affecting the eye of the storm 

Step five: You can create the Rasengan but instead of threading high-pressure streams of air through the moving sphere of compressed currents of chakra you will use the wind to constantly pull the air away from the center of the sphere before threading it through the sphere.

Taijutsu chakra manipulation/barriers

My second idea is the use of barriers. First, you create a small spherical barrier and increase the size of this barrier without letting air into this barrier. The expanding size of this volume with the zero increase in its internal mass will drastically drop the pressure inside this sphere. 

Luckily spheres are great for compressive forces which the outside atmosphere would be forcing down on this barrier. You can now, like a mantis shrimp, use taijutsu to land this barrier upon your opponent's body.

The smaller the initial sphere, the less air gets through your sphere, and the greater the size of the sphere you can produce the greater the volume of is displaced and the larger the shockwave when this bubble pops. 

This Jutsu should be fast to produce as you don't need to wait for natural changes and it might be possible to use this with the "Fist of a thousand hand technique log. However the more destructive the strike the further one needs to be from the implosion. 

The fact we are using a sphere as the method of delivery of this implosion shell with minimizing chakra use due to the sphere's high compression strength and impact of the sphere will concave the structure and create high-stress weak points for the bubble to bust mimicking a mantis shrimp's punch.

Step one: Create an airtight box of chakra. This can be tested by building this box around a small candle flame and waiting for the flame to snuff out.

Step two: Change this into a sphere the more perfect the sphere the greater. 

Step three: Create air-tight spheres you can practice expanding the size of the sphere without letting air into the sphere. This can be tested with the release of the sphere and the amount of wind it produces.

Step four: Shrinking the initial sphere and working on its total expansion. The shock wave will increase the further you ouch this

Step five: Attempting to do this more than once at a time.

Footnote: Next log I will be going in-depth on how you can improve your water Jutsu without increasing pressure by using chakra to affect viscosity.