Do you know why Japan's ponds are full of swan boats?

Sunaga began in 1887 as a shipyard in Meiwa, Gunma, a prefecture with no coastline. It built wooden ferries, later fishing boats and, from the 1930s, rowing boats for lakes and amusement parks. By the 1960s it was selling small motorboats that families could drive without a licence.

In 1974 Sunaga Yoshio was 34 and the firm's managing director. Boat accidents kept happening, and that year the law changed: engine boats now needed a licence. Children and families vanished from the water. NHK's "Chiko-chan ni Shikarareru" quotes him: "It became no business at all."

He copied the cycling craze that had taken over tourist spots and built a boat you pedal. In 1975 it was ready. NHK and the Gunma magazine Town Gunma both say it did not sell. It looked plain. Customers wanted something children would love.

Near the yard is Tatara Marsh, where swans come in winter. Yoshio went to look at them. "Pure white," he told NHK. "It looked wonderful to me." NHK dates his first swan boat to 1981 (Town Gunma says 1978). It did not sell either.

NHK says he kept going back to the marsh to watch the birds. About two years later he added a tail. Orders then flooded in. Town Gunma agrees on the boom but adds that whether the tail was the reason "is still not certain". Yoshio says the company would have struggled to survive without the swan.

• Inokashira Pond. Swan boats can be hired at the boathouse on the pond, the start of the Kichijoji tour. We could not confirm who built these particular boats.
• The tail. Look at the back of any swan boat. That is the part Yoshio says made the difference.

• NHK "Chiko-chan ni Shikarareru", 10 Jul 2020, narration transcript
• Asahi Shimbun, 15 May 2021
• Town Gunma, "Sunaga Co.", 22 Jul 2021
• Sunaga Boat, company site