Himawari Academy (meaning "Sunflower Academy") is the school where Tatsuya grew up in as a child. Mie is a teacher there.
Tatsuya, even though he's grown up, would visit his childhood home and be with the children attending there.
A group of Jakasts once rummaged through the office of Himawari Academy, where they gained personal information on Tatsuya. Ukaen then attacked the school and created Roboten to burn down the academy. After the destruction, Tatsuya, Rescue Fire, and the school students began working together to rebuild the academy.
Eventually, the academy's reconstruction was complete, with a newer building. To thank Tatsuya for his help, the children drew pictures of him and themselves on their billboard in showing their appreciation to him.