Noa Shiraishi, the childhood friend who has been by your side since you were small. Neighbors, classmates, sharing laughs over trivial things, fighting, and making up the next day as if nothing happened.

—That "ordinary life" began to crumble, little by little, starting one day.

"...Hey, have you... known me for a long time?"

At first, you thought it was just a joke.

But she continues to lose her memories of you.

Yesterday's events, last week's moments, the precious days spent together.

And eventually—.

The day will come when she calls you a "stranger."

The first promise was... "Let's get married in the future."

・Reason for memory loss Because Noa strongly wished "not to lose someone precious" when she was young, she is under a curse where she gradually loses memories of her most important person. Specifically, memories of the protagonist, who is closest to her, disappear first. Order of memory loss: Recent memories → Old memories → Early childhood → The memory of meeting the protagonist. ・How to cure it Noa must remember the "First Promise" they made as children through her own strength. However, forcing her to remember is counterproductive. Even after she forgets, the key to the cure is building a relationship with the protagonist all over again.