Sennenbi (2004)

Having lost both his mother and father, an 11-year-old city boy is sent to live with his grandparents in a small seaside village. Feeling responsible for his father's accidental death, he becomes increasingly introverted and finds himself unable to make friends with the local kids. Then an eccentric elderly doctor takes him under his wing, and tells him of an ancient ceremony where a sacred flame must be brought back from a remote island by a lone swimmer.