For me, Kozuki Hiyori was the biggest surprise of chapter 920. Not only because I didn’t expect Momo to have any siblings or other descendants of the Kozuki clan to still exist, but also because it greatly increased the chances for one of my favorite characters to appear in this arc.
I believe Hiyori could be Tashigi, and here’s how she could tie in with Wano’s present and past storylines.
1) Hiyori is NOT Tama (or Kuina)
Let’s get this out of the way first. I’ve seen many people speculate that Hiyori could be Tama, sent ~15 years into the future with Hitetsu aka – according to the theory – the mysterious kasa-wearing retainer:
No wings, no long nose… is that really Hitetsu?
I think this is not likely for a few reasons:
1-First of all, I think Kiku would have recognized Hiyori if she met her, or at least noticed a resemblance with her brother Momo (they’re the same age now) or to her parents if her appearance had changed growing up.
2-Second, why would Toki send her baby daughter to live in hunger and poverty for ~5 years before the prophesied heroes appeared? Wouldn’t it have been better to send her to a point in time after Wano was liberated so that she would re-appear in a rebuilt castle with her brother as Shogun?
3-Third, isn’t it too convenient that as soon as Luffy got to Wano, he met someone who not only knows Ace (which was already convenient), but is also Momo’s lost sister and a secret Kozuki?
4-Fourth, some say Tama is Momo’s sister because of the Japanese myth parallels they share (the kibi dango, “peach boy” etc.), but ignore the fact that the entire arc is based on Momotaro, not just Tama and Momo’s characters. Every new Wano character or place could have a connection to Momotaro’s story.
5-And finally: why would Hitetsu hide from her that she’s a Kozuki from the past – but at the same time has no problem with her overtly being a Kozuki supporter?
As for Kuina… she’s dead. We saw her corpse.
It would make no sense for Hiyori to be introduced and then reveal that she’s been dead for a long time. And Zoro’s dream wouldn’t make sense anymore if Kuina’s death was retconned. She has to remain an unreachable goal for Zoro in order for him to keep growing.
2) In support of Hiyori being Tashigi
We saw that Toki didn’t send Hiyori forward in time with Momonosuke and the others. I believe it’s because she was too young to face such a difficult adventure (from the way Toki is holding her, she seemed to be a toddler) and Toki had another plan in mind to keep her safe.
I don’t think she planned for her to remain in Wano, not even by hiding her somewhere. Toki probably knew what Wano was going to become under Orochi and Kaido’s rule, and as the last Kozuki, Hiyori would have been in constant danger of being found and killed – or married off to a Kurozumi.
It makes more sense then that Toki would have sent her daughter away from Wano; not in time, where she would find only the hardships of future Wano, but in space: perhaps off to a distant sea.
And if Hiyori never traveled through time and is still alive, judging from her being a toddler 20 years ago, now she would be between 21 and 24 years old. There aren’t many female characters that fit the black-haired, 21-24 year-old, parents-unknown requirements, and Tashigi is the only one that comes to mind. (I’m assuming Hiyori is black-haired by looking at Momo and because Wano is based on Japan.)
There are also a few things Tashigi and Hiyori have in common:
-They have similar haircuts. Hiyori seems to have short hair in a bob just like child Tashigi (who looks 6-8 years old here)
-They share a connection to swords. Hiyori is a descendant of samurai nobility and was born in the sword-country of Wano (whose national treasure is a sword); Tashigi has loved swords since she was little to the point that she’s called a sword nerd. We don’t know where her passion and natural skill with swords come from. In chapter 919 Momo has a practice sword just like Tashigi’s
-Tashigi is named after a bird, the common snipe. Hiyori is not named after a bird, but Toki is. Her name トキ, other than meaning “time”, is also the Japanese name of the crested ibis.
3) How Tashigi could get to Wano
Oda likes his mysteries, so it’s possible Hiyori’s identity won’t be revealed until the end of the arc. But I believe Tashigi/Hiyori may have a good reason to go to Wano and become an important character in this arc, and that reason is none other than her older-but-now-younger brother Momonosuke.
We know Smoker and Tashigi are with Vegapunk at the moment. And Vegapunk is responsible for the creation of the prototype artificial fruit Momonosuke ate, causing Momo a lot of trouble as he can’t control it.
We saw how Kaido’s smile users have problems and malfunctions when it comes their fruit abilities: Gazelle-man being out of breath after running, Holdem not being able to control his lion, animal parts growing in the most ridiculous places etc. Momo’s fruit is even a prototype smile. What if it has dangerous – or even lethal – side effects?
I can see Smoker and Tashigi tell Vegapunk about Momo eating the fruit and Vegapunk informing them of its side effects, causing them to rush to Wano to save him.
Even if this entire theory is wrong, Momo’s devil fruit is definitely a plot point that has to be addressed and solved during the course of the arc. And wouldn’t it be great for Smoker and Tashigi, who were there at the beginning of the Kaido saga, to be there at the end of it all? Everything would come full circle.
Could the reason Oda had Zoro wander off on his own be that he’s going to run into Tashigi (with Smoker and/or Vegapunk), since he’s the StrawHat that shares the deepest connection with her?
ps.: I forgot to specify that for this theory to make sense, I assumed Tashigi doesn’t know about her true origins. Otherwise she would have recognized Momo and Kinemon in Punk Hazard as people from Wano like her (although they never really had the chance to come face-to-face and interact during that arc). I imagine she grew up as an orphan and enlisted or was recruited by the Marines like many children as we saw in Big Mom’s flashback. On the other hand, it’s totally possible Momonosuke didn’t recognize her in Punk Hazard as she’s now 20 years older.
*Theory by TashigiTaisa