Lake Biwa is Japan's largest lake — a body of freshwater the size of a small sea, filling most of Shiga Prefecture just east of Kyoto. On the evening of August 6th, 2026, its southern shore in the city of Otsu becomes the stage for the fortieth edition of one of the most watched fireworks displays in Kansai. The 2026 program is built around a theme: Sengoku Discovery Shiga — the era of the warring states, played out again in fire. Twelve thousand shells rise from the water in two sequenced parts, joined this year by a drone show and coordinated laser work. Shells range from three-sun bore up to full ten-sun ones. Water starmines skim the surface and open low, using the lake itself as a mirror. Roughly three hundred and forty thousand people gather on the shore for the ninety-minute show. Most sit on the promenade of Nagisa Park, or in ticketed seating along the Otsu waterfront. The lake carries sound clearly. Reports return several seconds after the flash, bouncing between the water and the mountains on the far side. The choice of a Sengoku theme is not tourism copywriting. This particular water was central to the sixteenth century. The Azai clan held Odani Castle on the northern shore. Ishida Mitsunari, one of the losers of Sekigahara, was born in what is now Nagahama, further up the lake. Akechi Mitsuhide, who briefly killed Oda Nobunaga in 1582, held a domain here. Nobunaga's own castle at Azuchi rose on Lake Biwa's eastern edge; when he died the castle was burned within days. Much of what became modern Japan was decided within sight of this water. The main viewing zone runs along the lake front from Otsu Port to Nagisa Park. From JR Otsu Station it is a fifteen-minute walk south. From Keihan Biwako-Hamaotsu Station it is closer, about five minutes on foot. Both are direct rides from central Kyoto — twelve minutes on the JR line, an easy day trip that turns into an evening. Paid seats sell out early each year. Reserve in the spring if you can. A hotel in Otsu itself is difficult to book by June; consider staying in Kyoto and returning by train, though the final trains fill fast and pedestrian traffic through Otsu Station after the show is intense until well after eleven. Bring water and a light jacket. Late-summer evenings on the lake cool quickly once the sun drops, and the walk back to Kyoto by train is easier if you have not been dehydrated for four hours. Across the water, on the north side of Otsu, the wooded slopes of Mount Hiei rise darkly against the sky. Enryaku-ji, the great monastery Nobunaga famously burned to the ground in 1571, sits at its summit. During the fireworks the mountain remains one long silhouette. Every so often, when a large chrysanthemum shell opens near the peak, you can see the whole ridge lit for a half-second before the light fades. History pressed close to the surface for an instant, then gone.