Great catch. Given the identical wording, I think we have to assume that either Tsubasa is the narrator or is very closely connected to whoever is.
I actually think Tsubasa fits really well with what we know about the (first) beach narrator. As I posted previously, the stuff the narrator says about the tree indicates that they want to become a god or at least godlike.
Earlier in the event, the narrator indicates that they are unhappy with the "
God god" who made the world. They want their own world where they can do what they want, which includes helping their loved ones.
The narrator also seems to have empathy for the girls, which I think rules out Sekai/Pareidolia/The World Itself.
All of that seems very consistent with what we know about Tsubasa's motivations, wanting to have the power to manipulate people for benevolent reasons. In "Playing God" she even states that she wants to fill the role of a god who isn't doing their job.
Prior to the beach vacation, the "Cursded Birds" event opens with a monologue that I originally thought was just Sensei, but it actually makes a lot of sense that it's introducing Tsubasa as a new narrator. This is how the event opens:
The opening line is exactly the same as the game's first event ("Every Day I Grow Some More"). However, this time there is a different "first thing" that the narrator doesn't understand, so it's almost certainly a different narrator. I think the repeat of Narrator #1's opening line is meant to indicate a Narrator #2 is now introducing themselves. Also note that the narrator is describing the difference between childhood and adulthood, which implies they have a fair bit of experience with being an adult.
After that, the narrator starts talking about manipulation, which they seem to view as something that helps people
And the monologue closes with an indictment of "
God god", which I think is the only time outside of the beach vacation that a narrator uses that term in Chapter 1.
So in summary: possibly a new narrator, is/was an adult, views manipulation as a tool for good, and uses the same language as the beach narrator. Tsubasa seems like a perfect fit.
As for
how Tsubasa is able to act as a narrator, I suspect it has something to do with the wishing well (or if Tsubasa isn't the narrator, that's how they're connected).
The beach narrator wants Sensei to throw himself into the wishing well.
The last things that the Xoanon shows us in "Mother's Milk" is the Tsukioka manor sakura tree.
The Xoanon calls Sensei a puppet and says that others want to use him for purposes that the Xoanon agrees with. This could just be the gods, but Tsubasa has explicitly referred to Sensei as her puppet.
The beach narrator tells Sensei he can see more with his eyes closed, and the Xoanon says his eyes are closed to avoid being blinded.
Makoto says the same thing about seeing with your eyes closed in "Bluejay", and there's a good chance that she enters the wishing well since she gets Sensei's eyes. She says it before the suicide, however. Maybe she already has a wishing well connection from doing the same thing in previous resets, I'm not sure.
Edit: Oh and I forgot to mention, the beach narrator talks a lot about ticking clocks (and Rin starts hearing them). The room with clocks might be in the wishing well.