The official Pokémon movie website has updated. Translations follow:

Guest Voice Actor Announcement Part 2! Sachiko Kobayashi and Koichi Yamadera Are Back As Well!!

Following the announcement that Masachika Ichimura will be playing Mewtwo,
it's been decided that Sachiko Kobayashi and Koichi Yamadera will appear in the movie as guest voice actors as well.

Just like in the first movie,
Sachiko Kobayashi will play Voyager, the woman that manages the wharf,
while Koichi Yamadera will play the mythical Pokémon Mew.

---

Voyager/Voice: Sachiko Kobayashi
Manages the wharf, and is very familiar with the sea due to growing up by a port.

A comment from Sachiko Kobayashi


I feel extremely happy
to once again be able to take part in "Mewtwo Strikes Back Evolution" after 21 long years.

The original movie was a movie that nurtured kindness and sympathy,
and that moved lots of children with its adventure featuring their beloved Pokémon and friends.

I really want both those that were children back then, and for the children living in the present, to make sure they catch this legendary Pokémon movie, which has now undergone a further evolution, in the theater!!

---

Mew/Voice: Koichi Yamadera
A mythical Pokémon said to be the "origin" of all Pokémon, and which whereabouts Pokémon researchers all over the world are seeking for.

A comment from Koichi Yamadera


Since I was also hosting Oha Suta back when "Pocket Monsters the Movie: Mewtwo Strikes Back" premiered, I experienced how much of a social phenomenon the movie became both as an actor and as a reporter.
Since the movie is being remade in full 3D this time,
I feel like this is going to be an all new Pokémon movie even though we're actually back at the starting point... I'm very much looking forward to it.
I think this movie will remain in the hearts of both those that watched it way back then and the children watching it for the first time, and I really hope this will be the case.
I'm a bit worried about whether or not I'm still able to do the Mew voice, but I'll try my best with those high tones!!

Source: https://www.pokemon-movie.jp/news/?p=3614