This has been posted on the Last official website
it is the cover of the official song of the movie if I remember correctly.
Wikipedia : "The male duo Sukima Switch is performing the film's theme, "Hoshi no Utsuwa" (Star Vessel); producer Takuyuki Hirobe had asked the duo to make a song that invokes a gentle yet powerful outlook of the world in the making of the movie."
Tumblr is a mess right now, and I'd like to have some opinions here.