For 20 years, the nation of Wano was ravaged by Kaido and Orochi. However, Kaido was a foreign force, who only gained strength in Wano thanks to Orochi. To the people of Wano, Kaido was an evil, mythical foreign presence. But, Orochi was one of their own. Orochi betrayed his own people.
Orochi's clan, the Kurozumi, didn't try to destroy Wano once, but twice. And, this time, the nation became a impoverished, poisoned, barren, hopeless wasteland, where mothers were willing to kill their own starving babies. The people of Wano don't just hate the Kurozumi, they DESPISE THEM.
What words does Orochi use here specifically? "Apparently, even a child can be a criminal, if he happens to have the name Kurozumi." And this was BEFORE all of Orochi's crimes. Can you imagine how hated any surviving Kurozumi would be to this day?
Well... that clan was known for their purple hair. What child character in Wano do we know who fits that criteria?
Twitter post detailing O-Tama's parents gravestones
Tama is at this point more or less confirmed to be Kurozumi. Once people find this out... how do you think they'll react? Image Tama going to her parents' graves with Hiyori and Momo, and a royal escort. They are both shocked to see that one of her parents was a Kurozumi. While Hiyori and Momo keep it to themselves, the news quickly spreads through gossip amongst the other people in the palace, then Flower Capital, and Wano becomes furious, demanding that the last bits of Orochi's bloodline is erased. At this point, if Hiyori and Momo stood up for Tama, it could be very bad for them.
The people of Wano will want to exterminate the Kurozumi bloodline, permanently.
So... why not just age Tama up, and hide her that way?
Yep! Just like Momo, Tama will be turned into a 28 year old (this fits, as Tama and Momo have been tied together a lot through Wano). No one will expect her to randomly age 20 years and become an adult.
Tama is too young to escape a country with closed borders, that is currently dealing with outside forces like the Marines threatening to assault it. And, once an entire witch hunt is started for a Kurozumi, Tama will not be safe anywhere in the country.
Just as Hiyori's death was faked, Tama's death will be faked (possibly as a legit fake out death by Oda in the Manga itself, too), and they will claim she was murdered, when in reality Shinobu aged Tama up to allow her to live as a hidden ninja.
This set up Tama leaving Wano: once she sees the persecution she faces as a Kurozumi, she'll have even more reason to want to sail with Luffy, who is already fine with Tama joining.
Once the Straw Hats return to Wano, they will meet adult Tama who can now use Nijutsu, and take her with them to keep her safe from the crazy mutherfuckers in Wano.
I know you all hate this post, go ahead and roast me like I'm a Kurozumi.
