Nanairo no Mukou The Other Side of the Rainbow

Synopsis

After his sister's death, Ryousuke's parents separate. Feeling utterly helpless, Ryousuke runs away from home and finds himself on the other side of the rainbow in Nijigahara, a place where time doesn't flow and everybody is a child. But, will Ryousuke's presence in this seeming utopia, bring the fantasy world to an end and will Ryousuke ever get back home? (Source: MU)