The Hill Dyed Rose Madder (2008)

Nagase Jun'ichi rescues a girl he had never met before from certain danger. And as fate will have it, the next day a new transfer student named Katagiri Yuuhi joins Jun'ichi class, the girl he saved the other day.

Intending to thank him for what he did, they accidentally kiss, which starts the beginning of their tumultuous relationship...