Yamasachihiko and Umisachihiko (山幸彦と海幸彦)

Yamasachihiko and Umisachihiko is one of the anecdotes in Japanese mythology.
It is also commonly called 'Umisachi Yamasachi.'

Hoori (Yamasachihiko) swapped his hunting tools with those of his older brother Hoderi (Umisachihiko) and went fishing, but he lost the fishing hook. In order to look for it he went to Ryugu (the Palace of the Dragon King) as he was told by Shiotsuchinokami. He then married Toyotmahime, a daughter of Watatsuminokami (sea god) (Toyotamahiko), obtained the fishing hook, Shiomichinotama (tide flowing jewel) and Shiohinotama (tide restraining jewel), and he subjugated his older brother.

Storyline
Hoderi used to catch fishes large and small as Umisachihiko (fisherman), and Hoori used to catch animals large and small as Yamasachihiko (hunter). Hoori suggested to his older brother Hoderi to swap their tools. Hoderi was unwilling, but he decided to swap the tools just for a short period. Hoori tried to catch fish using his older brother's fishing hook (umisachi), but not only did he not catch even one single fish, he lost the fishing hook in the sea.
His older brother Hoderi also could not catch any animals, so he tried to get his tools back saying, 'the bounty of the mountain and the bounty of the sea cannot be obtained unless you use your own tools.'
When Hoori told Hoderi about losing the fishing hook Hoderi reproached Hoori.
Hoori made 1000 fishing hooks from his own sword, but Hoderi did not accept any of them saying 'it needs to be that particular fishing hook.'

When Hoori was sad and crying by the sea Shiotsuchinokami (god of ocean currents) came by. When Hoori explained the problem Shiotsuchinokami made a small boat and put Hoori on it, and he told him to go to the palace of Watatsuminokami (sea god). Hoori went to Watatsuminokami's palace as he was told, and when he was waiting there a female servant of the sea god's daughter, Toyotamabime, came out to get some water. Hoori asked for water, and the female servant poured water in a vessel and gave it to Hoori. Instead of drinking the water Hoori put in his mouth the jewel he was wearing around his neck, and he spat out the jewel into the vessel. The jewel got stuck to the vessel and could not be separated. The female servant brought to Toyotamabime the vessel with the jewel stuck to it, and she explained what happened.

Toyotamabime, who became interested, went outside, and when she saw Hoori she fell in love with him at first sight. Her father, the sea god, also went outside and said this man was Tenson (the grandson of the sun goddess) Ninigi's son Soratsuhiko (Hoori's honorific name), and he immediately married his daughter Toyotamabime to him. Thus Hoori lived with the sea god for three years.

After three years, Hoori remembered the reason why he came here, and he let out a deep sigh. The sea god asked the reason for the sigh, so Hoori explained the reason why he was here. The sea god gathered all the fishes and when he asked if anyone had a fishing hook he found out that it was stuck in the throat of a red porgy. The sea god gave Hoori the fishing hook as well as Shiomichinotama and Shiohinotama, and he told him as follows. Keep your hands behind your back when you give the fishing hook back to your older brother saying "this fishing hook is obobari, susubari, majibari, urubari (a fishing hook that makes you depressed, a fishing hook that makes you anxious, a fishing hook that make you poor, and a fishing hook that makes you dumb)."
If your older brother makes a rice field on a higher ground, then make yours on a lower ground.'
If your brother attacks you, then use Shiomichinotama to drown him, and if he suffers and begs for forgiveness then save his life with Shiohinotama.'
He put Hoori on a wani (crocodile, refers to a shark) and took him back home. That wani is now called Saimochinokami.

Hoori returned the fishing hook just as the sea god told him, and he made a rice field as he was told. Because the sea god controls water Hoderi's rice field did not get water, and Hoderi eventually became poor. When Hoderi attacked Hoori, Hoori used Shiomichinotama and drowned him, and when Hoderi suffered and asked for forgiveness he took out Shiohinotama and saved his life. As this was repeated Hoderi surrendered, and he said he would serve Hoori and protect him day and night.

Hoderi is the patriarch of Hayato, and even to this day the people of Hayato serve him by acting out how Hoderi drowned.

Interpretation
Legends that take the form of visiting a foreign land by chasing a lost fishing hook or a hunting tool and getting one's revenge on the owner by finding and obtaining these items can be found in various places throughout the world.

Furthermore, stories about confrontations of a mountain god and a sea god causing a large-scale flooding can be found in various places throughout the world. In Japanese mythology, the fighting between the people of Tenson and the people of Hayato was added.

This story is a precursor to senkyo-tairyu-setsuwa (stories about sojourn at an area where hermits dwell), stories of marriages between gods and humans, and Urashimataro