If you're looking for anime similar to Hoshi wo Ou Kodomo, you might like these titles. All recommendations are made by Anime-Planet users like you!
One day, the young Wataru decided to visit a haunted building in search of a ghost, but ended up meeting a boy by the name of Mitsuru instead. He has the ability to use magic, and tells Wataru about another world where the wondrous Goddess of Destiny lives – a goddess who can grant any wish. The next day, Wataru returns home only to discover that his parents are getting a divorce, and subsequently, his mother ends up in the hospital in critical condition. In an attempt to fix his family, Wataru goes back to the building and sets off on a journey to the magical world in order to gather five jewels, and ultimately, to gain an audience with the Goddess of Destiny...
Both movies are directed by Makoto Shinkai, so they share similar elements in terms of characters and pacing, the animation in both is stellar, and isn't too dissimilar from each other either. Aside from that, they don't have too much in common, but a fan of Shinkai's works will appareciate both movies.