Kimi no Iru Sekai Shikairanai

The bright spot in Futaba's lonely childhood was Yuki, a pretty boy who helped him when he was lost and would magically appear to relieve his tears. One day, Futaba, sad at his parents continual neglect runs away and asks Yuki, "Do you hate me too?" Yuki responds with a kiss and then disappears. Years later his father announces that his brother, Kazuyuki, from a previous marriage will be living with them. Yuki has returned to Futaba but the gentle and kind boy of the past has been replaced by a cold and beautiful stranger.