Final Getsuga Tenshou is Quincy Letzt Stil
I will now lay out all the arguments as to why Final Getsuga Tenshou is really Quincy Letzt Stil. Its a theory by definition, because it was never properly explained within the manga as to what Final Getsuga Tenshou really is.
- Letzt Stil is german and directly translates into "Final Style". Kubo calling it "Final" Getsuga tenshou has a striking resemblance here.
- Both Letzt Stil and Final Getsuga Tenshou give an extremely large power boost, last temporarily, and ultimately result in the user losing all their powers afterwards.
- Both techniques are preceded by the exact same mechanism. The user first has to merge his weapon with his hand. Uryuu had to wear the Quincy glove, which is really a weapon (the bow), while Ichigo´s sword started merging with his hand via glove.
- Prior to unleashing their final attacks, both users lose their weapon´s physical forms, and the weapon instead manifests as spirit weapons. In the case of Uryuu its just the arrow.
- Isshin is not the person who taught Ichigo Final Getsuga Tenshou (a popular theory is that it is a Shiba technique). Isshin taught Ichigo who could TEACH him -> Zangetsu. And we know that Zangetsu is really Yhwach. Yhwach teaching a shiba clan technique? Unlikely. Yhwach teaching the final Quincy power up? Very likely.
- Aizen was transcendental at the point where Ichigo faced him. None of the other shinigami had a remote chance the second Aizen started transcending, beginning with his Chrysalis form. The combined power of Isshin, Urahara and Yoruichi was easily bested. So Ichigo by definition, cannot win with just a regular shinigami technique, it wouldnt be transcendental. Ichigo needed to tap into his hybrid powers. Yhwach gave him the final Quincy power up. But prior to that Yhwach actually merged with Ichigo´s vasto lorde form, so Ichigo was really tapping into all his hybrid powers. Its a hollow powered up Letzt Stil (which is why it appears dark instead of light)
- Just before the fight, Aizen had his little chat with Ichigo, where he specifically alluded to the fact that Ichigo wasnt just a shinigami. But just before he was able to mention it, Isshin arrived. He was obviously gonna say "Quincy". So the concept of Ichigo also being Quincy wasnt introduced in the TYBW arc. It was already introduced just before Dangai, foreshadowing the arrival of Quincy powers:
- Aizen actually also used Quincy powers. The entire series he was talking about transcendending Shinigami by breaking down the barrier between shinigami and hollow. But when he finally used hogyoku for himself, for some reason his first forms looked nothing hollow like. Instead they looked angelic and merged his weapon with his hand (sound familiar?). The holy form is actually that of a quincy. He was first breaking down the barrier between shinigami and quincy, and Butterfly aizen in reality is a Quincy Shinigami Hybrid, who is specifically made to look holy by Kubo. Once he transcends even further and merges hollow powers in, he has a angelic looking hollow instead:
Its rather consistent, and any inconsistencies could be attributed to the red herring factor:
Kubo not wanting to fully reveal the true nature of Ichigo´s powers just yet and using vague explanations.
On a sidenote its also worth noting that Lille Barro has a very similar holy form to Aizen, and both their teleportations look extremely similar as well:
u/gh_0un — 9 hours ago