Why the sandwich in Japan is triangular

March 13th annually is one of at least two days dedicated to the sandwich in Japan! The other, that I know of is November 3rd, and both days were chosen for wordplay on the digits of the dates. On March 13th, 3/13, the 1 is literally "sandwiched" between two 3s, turning it into a lighthearted visual pun.

Although the group that created the anniversary is unknown, the day has become a fun excuse to appreciate one of the world’s simplest and most adaptable foods. In Japan, sandwiches have their own rich history. The country’s first recorded sandwich sold as an ekiben appeared in 1892 at Ōfuna Station, marking the beginning of a long relationship between sandwiches and travel.

However, it was a development in 1961 that both literally and figuratively shaped the future of Japan's sandwich. A small shop near Myōgadani Station introduced the triangular, cut‑open sandwich style that we've all come to know in Japan. It was an innovation inspired by a customer who wished for “a sandwich where you can see what’s inside.” Initially, the shop patented the idea but released it five years later, allowing the style to spread nationwide.  And thanks to that, we can now all enjoy Japan's picture-perfect triangular sandwiches.