Okay, that’s a tough one because honestly, Naruto x Shikamaru isn’t exactly a mainstream pairing, so finding a proper slow-burn is like looking for a specific needle in a haystack. I’ve read a few over the years, but a lot of them either rush the romance or treat Shikamaru like he’s just the smart guy who magically falls for Naruto’s sunshine routine without any of the friction that makes the dynamic interesting.
There’s an older one on Fanfiction.net called 'Shadows and Sunshine' that comes to mind—it starts post-war with them having to work together on diplomatic stuff. The burn is incredibly slow, almost glacial, focusing mostly on political maneuvering and trust-building before any real feelings surface. Some readers dropped it because the romance took over 30 chapters to even hint at, but I appreciated the patience. The author really dug into Shikamaru’s canonical aversion to effort and how Naruto’s persistence could wear that down logically.
Another on AO3 is 'Calculated Risks' where Naruto’s the Hokage and Shikamaru’s his advisor, and it’ s all about suppressed tension during long strategy meetings and the occasional life-threatening crisis forcing emotional honesty. The pace felt earned, but the author abandoned it after about 50k words, right as things were getting good. So many promising fics in this ship just vanish.
Honestly, your best bet might be to filter for Naruto/Shikamaru on AO3, sort by word count, and look for tags like ‘mutual pining’ or ‘emotional intimacy’. Skip anything tagged ‘smut’ or ‘fluff’ right away if you want a genuine slow-build. The real gems are usually hiding in the mid-range kudos stories, not the super popular ones.