Yamata-no-Orochi and the sword

Foundational Shinto myth of the serpent and the imperial sword

Susanoo, thrown out of heaven, comes down to Izumo on the upper Hi River and finds an old couple, Ashinazuchi and Tenazuchi, weeping over their last daughter. A serpent with eight heads and eight tails has taken seven daughters and is coming back for Kushinada-hime.

His method is not heroic in the usual sense. He turns the girl into a comb and puts her in his hair, has the parents brew eight batches of strong sake, builds a fence with eight gates and sets a vat at each. Orochi arrives, puts a head into every vat, drinks all eight and falls asleep. Susanoo then cuts it to pieces. His blade chips against the middle tail, he opens it, and inside is a sword: Ame-no-Murakumo, later called Kusanagi. It becomes one of the three imperial regalia of Japan.

The scholarly readings are what make this worth a pin on a map rather than a page in a book, because they are all geographic. The serpent is widely read as the Hi River itself, which flooded badly and repeatedly before its course was redirected in the Edo period, and Kushinada-hime's name means something close to Lady Wonderful Rice Paddy, which puts the story squarely on the argument between a river and the wet-rice fields beside it. The annual sacrifice of a daughter is the annual cost of living below that river.

There is an iron reading too. Izumo was a major iron-producing region, and some scholars connect the myth to metalworking arriving from the Korean peninsula, with the sword found in the serpent's tail standing for iron sand exposed in the riverbanks by landslides.

The pin is on the Izumo country in Shimane. Go for Izumo Taisha, the river, and one of the oldest continuously told stories in Japan.