Two Happy Genius Heroes by muckraker (grendelity)
Sword of the Stranger (anime, 2007)
Rated G
Gen
Friendship, Family of choice

Author's Summary -- Nanashi and Kotarou, after the dust has settled. Sort of. There's a lot of dust to settle.

Rec -- Here's what I wrote in a comment to the author:
"I came looking without much hope for something that picked up where the film left off. I consider myself lucky that you wrote in this 'fandom' (can I call it that when there's one fic on AO3) and more importantly that your story is so enjoyable to read with a hopeful/melancholy tone just like the film. Thanks so much for giving me a bit more of Nanashi and Kotarou. Just right and very satisfying."