Silent Blue

When Aoko was four, a meteorite struck her town. It then rained for twenty days straight, and the crater became what's now known as the Twenty Day Lake. Two decades later, Aoko can't remember the day the meteorite fell, or anything of her life in the town beforehand. And so she dives deep into the lake, searching for that something in her memories that she can't let go of…
A 1-volume manga.

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Author's Twitter: @icori\_a