Summer Break Spent with a Vampire

As Akari's summer break has finally begun, she wracks her brain to come up with fun, summery things she can do together with Sophie. However, the ocean or anything outside are all a bad fit for a vampire like Sophie. Then she has a moment of clarity and realized that a firework festival is at night and a summery activity, so she immediately begins preparing yukata. Erie and Hinata and join them to go to the festival, however...