Story
The protagonist, Ichikawa Yuushi, ends up staying at his childhood friend Nanamiya Ayame's family home.

One night, Yuushi heads to school alone at night as Ayame's messenger.

After safely completing his mission and on his way home, Yuushi notices something.
--Something is following him.

He desperately tries to escape, but as he is cornered by an approaching shadow, he hears Ayame's voice.

"I will definitely protect you, Yutchi!"

Ayame drives away the shadow with a flash of her flash, and learns about the role and enemies that the Nanamiya family has inherited for generations.

"To put it simply, the Nanamiya family is a clan that has been exorcising impurity for generations."
The existence of "impurity" that harms people
The Nanamiya family exorcises it

Ayame's family is a shrine, so she helps out as a "shrine maiden." That's how Yuushin thought of it, but it seems that it wasn't that simple──

Ayame, who is tasked with purifying the "impurity"

Yuushin doesn't want to let Ayame go to dangerous places alone

Memories of a summer when the two chose to fight the "impurity" together

Translated from https://www.dlsite.com/maniax/dlaf/=/link/work/aid/vndb/id/RJ01084292.html