Touhou - Sakuya to Sonogo (Doujinshi)

The protagonist who had strayed into Gensokyo was found collapsed and got rescued by Sakuya Izayoi.

After he returned to the human world, he had a realization about how humans didn't know when they were going to die. Aiming to live without regrets, he goes to confess his love to the person he likes, but gets rejected. At that time, he was comforted by Sakuya, who had come to bring him something he left behind.

What will the protagonist, who had entered into a physical relationship with her, do next?

(Source: DLsite)