Queen Emeraldus

Emeraldas navigates the sea of stars—and swears to do so until the flame of her life is extinguished. Aboard her ship, the Queen Emeraldas, she sails in search of a certain object, and along the way encounters the passions and tragedies of those who dare brave the infinite reaches of space.

(from ebookjapan):

On the planet Jera, a young woman met her lifelong friend, a ship named the Queen Emeraldas. Huddled together and covering for each other, they set off on a journey through space...

No one knows why or what they continue to wander the universe in search of. On the red sands of Argyre, Emeraldas meets a boy named Hiroshi Umino, who has lost his spaceship. Emeraldas feels some kind of strong fateful bond with this boy who has an indomitable fighting spirit...

Official English