Thus far it has been shown that Hiyori is a master at disguising her true personality. For years she played her part as Komurasaki, and for whatever reason, I think she’s been hiding her true ability as a swordsman.
There are several reasons why I believe she’ll soon join the war as a formidable samurai.
- Her whereabouts are currently unaccounted for. It’s extremely strange we don’t know where she is or what she’s doing. Oda wouldn’t just leave her out after introducing her, and I’m sure she’s being saved for something down the road.
- An interesting facet of the culture in Wano is that there are no women samurai (yes I know we have O-Kiku, but she was a boy originally). I find this striking because One Piece isn’t at all devoid of strong female characters. Where else have we seen this trope? That’s right, we saw it with Kuina at the beginning of the story. Zoro told Kuina that being a woman had nothing to do with it and that she could become a powerful swordsman despite that. Perhaps Hiyori will be just that in Wano, a true samurai.
- Hiyori was raised by Denjiro in a consistently hostile and dangerous environment. I can’t imagine that one of the most powerful samurai in Wano wouldn’t raise Hiyori with the ability to defend herself. It would make perfect sense, and her ability to disguise her personality might extend to her latent abilities, which would explain why nobody could sense she was secretly strong.
- Oden’s other sword was left behind. We know Zoro has Enma, but Momonosuke’s sword Ame no Habikiri was left with the swordmaker. I can see Hiyori picking it up as a sort of placeholder for Momonosuke, and honoring Oden by fighting with it.
- With Yamato now having entered the story, we see that Kaido’s daughter is an insanely powerful warrior. It would be great parallelism if Oden’s daughter was the same, and it would make plenty of sense.
- Momonosuke is too young to be Shogun of Wano even if they beat Kaido. Hyori could definitely prove herself as being nearly as powerful as Oden, and take that mantle while Momonosuke still grows.
- Oda has been consistent with making any woman called most beautiful incredibly powerful. Boa Hancock is a Warlord and one of the strongest female characters in One Piece. Shirahoshi is an Ancient Weapon. Hiyori is clearly hiding who she is. She will more than likely appear at the beginning of Act 4. Ame no Habakiri is the sword that will cut Orochi in Japanese mythology. She said she wants to kill him(there’s an ongoing theory according to which Fukurokuju will revive Orochi) and she will.
*Theory by Schlogin