Great Gidayu

It's summer and nine-year old Masao (Sekiguchi) has no one to play with. He decides to go in search of the mother he has never met. Kikujiro (Takeshi), a brash, loudmouthed and irresponsible adult, agrees to accompany him on his quest. Ultimately, the two of them end up at a destination that neither of them could have imagined. (Sony Pictures Classics)

A young girl named Mitsuki receives a ticket for a bus tour from her uncle. The tour appears to be normal (except that everyone appears to be quite somber), but Mitsuki learns its true purpose. All passengers and the tour manager have a suicide pact to send the bus over a cliff so that the families can collect the insurance money. (imdb)