This is a major summer event in Nagai, themed around its water sources, which have been selected as one of the '100 Best Water Villages.' The daytime Water Festival is held at the 'Kurunto' venue, while the evening 'Mogamigawa Fireworks Festival' takes place at the Mogamigawa Riverside Green Park. Spectacular fireworks are launched from the opposite bank of the Mogami River, painting the summer night sky and water surface with brilliant colors.