Kirk here with information about an upcoming event in Yatsushiro. I checked the Japanese side of the site and apparently it’s too late to get reservations for the paid seating but there should be lots of free spots on the grounds from which you can enjoy the show in the sky.
Event title: The 35th Yatsushiro National Fireworks Competition Festival Date: Oct. 15th, 2022 (Saturday) Location: The flood plain of Kumagawa River in Yatsushiro City (upstream from the Shin Hagiwara Bridge)