The strait divides two islands. Honshu on one side, Kyushu on the other. Between them, a narrow band of water no more than seven hundred meters across at its tightest — the Kanmon Strait. On the evening of August 13th every year, both banks light up at the same time. This is the only fireworks festival in Japan where the show is fired from both sides of a strait at once. Fifteen thousand shells rise from Moji in Kitakyushu and from Shimonoseki on the Yamaguchi shore, competing across the water, framed by the silhouette of the Kanmon Bridge overhead. Chrysanthemum shells. Underwater fireworks skimming the surface. Set pieces that spell out patterns above the tanker lanes. The number of spectators reaches roughly seven hundred thousand each year — three hundred and fifty thousand on each side, watching each other watch. The event began in 1988 to mark the sister-city relationship between Shimonoseki and Kitakyushu, and something of that gesture remains: two cities facing each other across the water, holding a conversation for one night, in light. Before and after the launch there is a stage program on the Moji side. Local musicians play. Sea wind carries the sound sideways. Ships that would normally push through the narrows are held back for the evening, and the water — usually one of the busiest shipping channels in East Asia — goes still. The main viewing area on the Kyushu side runs along the western waterfront of Moji, in the Moji-ko Retro district of red-brick warehouses and Meiji-era customs houses. From JR Moji-ko Station it is a ten-minute walk. On the Honshu side, viewers gather at Arcaport, a short shuttle ride from JR Shimonoseki Station. Both sides fill by early afternoon. Ticketed seats sell out months ahead. Getting home is its own event. The last shinkansen fills fast. The Kanmon pedestrian tunnel, an underwater walkway connecting the two coasts, stays crowded until well past midnight with people crossing on foot from one prefecture to another after the show. There is something in the geography that makes this particular festival hit differently. This is the water where the Taira clan drowned in 1185, ending Japan's first samurai war. The waterfront at Chofu, just south of Shimonoseki, is where Takasugi Shinsaku rallied troops in the 1860s and helped launch the Meiji Restoration. Moji-ko itself was the country's window to the continent in the early twentieth century — coal, silk, and steamships passing through on their way to Shanghai and Dalian. For most of the year the strait is a working channel, indifferent, tidal. On this one night the water carries only sound: two cities firing shells at each other in the friendliest possible way, the reports bouncing back and forth between the cliffs for a full second before fading.