Tsubasa Kamiyashiki knows her childhood friend Hiyori Tamaki's secret. She causes a mysterious phenomenon called "Amazakura," where pink petals fall from the sky when she is happy, and black petals when she is sad. Hiyori is someone special to Tsubasa, as she has been secretly observing her heart and understands her the most.

In the summer of her second year of high school, Tsubasa, who has become estranged from Hiyori due to a certain "incident," meets transfer student Ruka Shishibuki. Ruka befriends Tsubasa to learn more about the mystery behind Amazakura. The encounter between Tsubasa, who has been secretly protecting Hiyori, and Ruka will reveal the feelings these girls hide inside their hearts.

(Source: Official Site, translated)