The official Pokémon movie website has updated. Translations follow:

Story

Do you know
how these two met?

Satoshi and Pikachu are currently the best of partners.
But the truth is, their initial meeting went as badly as it could possibly have!

A Pikachu that won't listen to Satoshi,
and an unskilled Satoshi that wants to befriend Pikachu:
Can these two become true partners?

On the day they set off from Masara Town,
the two swore an oath as they looked up at Houou flying across the sky:
"Let's go meet it together one day!"

And now this duo's adventure begins, guided by the shining rainbow-colored wings!

"Why won't you enter the monster ball...?"

Teaser and trailer

The site also updated with a new teaser and a new trailer for the movie:

Teaser 2:

Trailer 1:

Source: http://www.pokemon-movie.jp/story/ and http://www.pokemon-movie.jp/trailer