The Burden of Guarding Time

Setsuna is not one for interfering with the passage of time, but when she sees a horrible future in store for her Queen, she decides to change Usagi's past to try and save her future. Except both times, no one ends up happy. Usagi x Mamoru, Mamoru x Rei and slight Setsuna X Minako. Changed to M because it's a more appropriate rating. Character deaths warning (sort of).