Amanozako (Kasumi)

Ad Astra is a personal Taijutsu technique of Yuki Kaneko's that uses the Eight Gates. This technique symbolizes the type of genius Yuki is and her desire to always break past her limits and what is possible, which is why she gave it the name she did. The few who have witnessed the technique can't help, but be in awe in the level ingenuity it would take to come up with this and the level of skill it would require to perform it successfully.

Description
After learning she could focus the power of Eight Gates to a body part to keep the rest of her body unarmed and amplifying its benefits because of how concentrated the power is, Yuki began experimenting just how much she can concentrate the power. Eventually she managed to concentrate the full power of the seventh gate into her pinky finger, which is where this technique was born from. Yuki raises her right arm and extends it forward keeping the arm steady by grabbing the wrist of that arm with her other hand while bending her right pinky back with the right thumb as if to flick it. Staying in this position she opens the seventh gate and uses her control over her tenets granted to her by Gentle Fist to direct, harness, contain the rush of chakra that comes from this into a more focused point: her pinky finger causing the physical limitations of that finger to be utterly shattered. Finally, she flicks her pinky finger with tremendous force to unleash a pressure wave with tremendous power. So much power in fact that during one of her spars with Matatabi the pressure wave generated was strong enough to launch the large tailed beast with great force and deal devastating damage to the area in the process.

This technique does have one big drawback. Just as the benefits of the seventh gates are made more extreme so is the side effects. The pinky she uses to perform the technique will be greatly damaged to the point that the last time she used the technique it took months to heal even with her regeneration. Furthermore, whenever she tried flowing chakra to that hand in those months it put her in great pain suggesting that this technique puts an unhealthy level of toll on the pathways and tenketsu involved.

Ad Astra is certainly a technique that Yuki should be throwing around whimsically. Although it is rare for her to open all seven gates, she does use a less drastic version of the technique by opening one or two techniques. It may not be nowhere as near as stronger as the original, but at least this version of Ad Astra comes with very few side effects.

Regardless of how much power she puts into the technique Ad Astra requires a tremendous amount of Taijutsu skill and control. What surprised Matatabi the most wasn't its power, which was impressive, but the fact that Yuki was able to use it at any level. Saying that claiming even a great Taijutsu master would find this technique more than just difficult to perform would be an understatement and further suggesting that the tiniest mistake could end very badly for Yuki.

Trivia

 * Yuki usually chants "Non est ad astra mollis e terris via.” meaning "There is no easy way from the earth to the stars" while using the technique at full power. Matatabi believes that this may be her Nindō.