"Even without my memories, I won't be scared. As long as you're there to remember for me."
So said the girl with 『no future』.
If a future is made by repetition, stacking up the days, then indeed a 『future』 she lacked.
『Anterograde amnesia』.
Also known as 『repeating disease』, a curse that eats away at your memories and future as they form.
"If someone makes a mistake, they correct it. Not just repeat it over and over... No one should be forced into doing that."
So said the man with 『no past』.
And thus the two set out to recover the 『past』 and 『future』 that they respectively lack.
All the while not realizing they've already entered the 『repeating world』...

[Translated from The Official site]