The Sanzu River (三途の川 Sanzu-no-kawa), or River of Three Crossings, is a Japanese Buddhist tradition and religious belief similar to the River Styx. It is believed that on the way to the afterlife, the dead must cross the river, which is why a Japanese funeral includes placing six coins in the deceased's casket.
The Sanzu River is popularly believed to be located in Mount Osore, a suitably desolate and remote region of northern Japan.
According to the Soka Gakkai, traditionally, people are said to cross on the seventh day after their death. It has three crossing points: a bridge, a ford, and a spot where there is only deep serpent-infested water. Where one crosses depends on the weight of one's offenses while alive. Those who performed acts of good while alive cross over a bridge adorned with seven precious substances. Those whose karmic balance of good and evil is relatively even cross at a ford. Those who committed great evil must wade through deep water infested with hideous serpents. On the bank, a male demon and a female demon dwell under a large tree. The female, named Datsue-ba, strips the dead of their clothes, and the male, named Keneō, hangs the clothes on a branch of the tree to determine the weight of their offenses. There is also a popular saying: "If you take that much money, you're going to drown in the Sanzu River".