Shadow Star, Volume 2: Darkness Visible — Mohiro Kitoh

Teenagers Shiina and Akira have become fast friends, due in no small part to their bonds with two shape-shifting alien star-creatures. But their small friends are not the only visitors from beyond, nor are Shiina and Akira the only kids connected to them. Roaming the skies are powerful and dangerous Shadow Dragons, and one is linked with a schoolmate of the girls, a malevolent boy with murder in his heart -- and a deadly, flying dragon at his command to make it happen!