I'm linking the Mamoru-centric fanfic I've been talking about below. This takes place not long after the Makai Tree arc when he had just regained his memories. The story is slated to have an introspective, almost mysterious tone as Mamoru figures out who he really is.
Mamoru Alone - Chapter 1 - DistinctStoryteller - Bishoujo Senshi Sailor Moon | Pretty Guardian Sailor Moon [Archive of Our Own]
Mamoru Alone - Chapter 1 - DistinctStoryteller - Bishoujo Senshi Sailor Moon | Pretty Guardian Sailor Moon [Archive of Our Own]