Prologue

"All that is past.. will return to Nihility."
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'Raiden Bosenmori (guardian of the river?) Mei.'. A name she shouldn't have remembered in this state.. Strangely, this name evokes familiar memories to her.

When she, lost in an extinct planet, finds a dream bubble, it awakens similar memories to her name.
Thus, she awakens in this dream bubble.
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This is an AU requested by someone, so there will be some deviations from the canon lore of Acheron.