2 Works in Mamiya (Fist of the North Star)
Mamiya hates birthdays, and Airi attempts to change that. (Rape warning tag is for discussion/nonexplicit flashback.)
Ken's not paying attention to Rei or Mamiya, and things get awkward on multiple levels. Surprisingly as far as things I write go, this is the setup to what that sounds like. Unsurprisingly, it's also trans fic and body/gender issues rather than straight up smut. Still NSFW and adult.