Important Update:
I have changed Yu-Gi-Oh!: Mirage's rating to explicit on ao3. Reason being is that realized going through what I want to do for Arc 1, and some of the others arcs, it is going to get dark and graphic in terms of violence, gore, and (maybe) physical/psychological abuse.
No, there will not be sexy time (at least I don't think so, anyways); I plan on more so focusing on the story aspect of it. The only reason why it is rated this way is due to the descriptive and possibly gore-like nature will add to some scenes that deserve it to really enhance the "horror" factor.
Takahashi in the beginning of his manga did incorporate horror themes, but I want to express the seriousness of this story. I will definitely give warnings at the beginning of chapter's for it, so that way people who are uncomfortable with that kind of content may skip it, and I can give a TLDR at the end.
Will of the Wisps might also be changed to explicit due to the violent nature, also, on ao3? But I'm still unsure at this time, given how I've been going about the fight scenes. Maybe at the end of the story might considering what I want to do? I don't know, yet.
If y'all have any advice regarding ratings with ao3, I'd appreciate it. But if I'm going about this the right way, let me know!