Natsu no Arashi!

Yasaka is a 13-year-old boy spending his summer vacation at his grandfather's house. While visiting a local store, he meets Arashi, a 16-year-old girl who possesses supernatural abilities. After Yasaka intervenes to protect Arashi from a man claiming to be her family's emissary, they flee together and Arashi begins staying with his grandfather's household. As Yasaka becomes more familiar with Arashi, a 60-year-old photograph of her and a woman named Kaja sparks the introduction of Kaja, who, like Arashi, appears to be ageless.