With Yamato resolving to become Kozuki Oden, could they become a Nitoryu user? Yamato has already donned a style similar to Oden’s in terms of their outfit and if they had two blades, I believe they would also wield them. Just like Oden, Yamato wouldn’t need to follow a set Nitoryu style and could develop their own. Yamato has already shown they have experience with their Kanabō and if they were to attain two blades, they could incorporate their existing fighting style through the swords to develop their own variation of Nitoryu, just like Oden.
Once Yamato and Momonosuke befriend each other, I wonder if Momonosuke will eventually bestow onto Yamato, the Ame no Habakiri. At this point in time, Momonosuke does not believe he is ready to wield it and given their current conflict with the Beast Pirates and Big Mom, Momonosuke may end up offering the blade that once belonged to his father, Oden, to Yamato as a weapon to wield against Kaido and Orochi.
Yamato could use that blade to help defeat Orochi once he reappears and transforms into his Yamata no Orochi form (he ain’t dead). Orochi also wields a sword (the one he tried to kill Toko with) and that could be a Meito that he had Tenguyama Hitetsu forge at some point in the past. Even if Hitetsu did not specifically forge a sword for Orochi, Orochi could have still claimed one of Hitetsu’s blades as his own after he became Shogun. It could have been that event that led Hitetsu into hiding. Orochi’s sword could potentially be the Ame no Murakumo no Tsurugi (“Heavenly Sword of Gathering Clouds”). In the Yamata no Orochi tale when Susanoo used the Ame no Habakiri to chop up Orochi into small pieces, he ended up discovering a blade in the fourth tail of the beast. The sword was the Ame no Murakumo no Tsurugi. If Yamato is destined to fight and help defeat Orochi, Yamato could discover Orochi’s blade when Orochi is defeated. Yamato could claim that as their second blade for their Nitoryu style. If Yamato’s mother were part of the unrevealed ‘avian-race’ Hitetsu belongs to, he may have known her and as such have no issue with Yamato using the swords he crafted. Once in possession of the blades, Yamato could help Luffy against Kaido by slicing though the heavens and cutting the clouds Kaido uses to fly in his Dragon form. At some point it would also be fitting for Yamato to inflict a physical wound onto Kaido – with the Ame no Habakiri.
In addition to using the two Meito, Yamato could also continue using their Kanabō. The reason for wielding two different weapon sets could stem from the dual identity Yamato is currently in a state of collision between. Given a situation, Yamato could choose to fight as the child of Kaido using the Kanabō or if they feel like Kozuki Oden, they could choose to use their Nitoryu style during those moments. Yamato’s conflict between their two identities could serve as their quirk (if they were to become a Straw Hat nakama) and be the struggle they have to eventually overcome. To not be lost in the strife and uncertainty of their current state of mind. If Yamato were using Kozuki Oden’s identity to mask their own weaknesses and vulnerabilities, the moment they have to face themselves could be a deeply inspiring moment with much emotional resonance. Yamato will need to find out who they really are and this could be someone that embraces being both the child of Kaido and the inheritor of Oden’s will.