 If you liked
W: Wish
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 ...then you might like
Little Busters!
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Both: based on a VN, protagonist has memory loss, and "something is not right with this world" is pondered a lot. It's hard to give more information without spoiling both series but VN players of Little Busters! and fans of Key's works will understand the reoccurring theme. And that theme is in W: Wish.