After winning a lottery in the shopping center, Kaito, Mitsuo, Fukuta, Ai, and Kaito's grandfather Zōan head to a hot spring inn, where Hana and the Gamitsui Corporation are coincidentally helping out. Later that night, Kaito accidentally breaks his Bankfon G after being spooked by Ai. Afterwards, Kaito runs into Hana, who explains she is trying to help out the inn, which holds a lot of memories for her, to keep it from being sold to a developer, before accidentally spraining her ankle. The next day, the developer, Ageo Sokoo, comes and smashes the inn's entranceway, trying to coerce the owner into selling the inn. Wanting to protect Hana's memories, Kaito challenges Sokoo to a Hero Battle against his Hero Suit, Heavy Builder, with the inn on the line.