Most Tokoyami and Shoji fics I run into lean hard into the 'stoic guardians understanding each other' vibe. They're both the quiet, physically imposing guys who watch everyone's back, so a lot of writers explore that shared sense of duty. Found family within 1-A is huge—scenarios where they're the last two up after a training exercise or paired on a night patrol. There's also a surprising amount of body image stuff, but from a totally different angle than, say, Midoriya. It's less about insecurity and more about the practicalities and odd intimacies of having non-standard bodies—Shoji helping preen a feather Dark Shadow messed up, Tokoyami being one of the few who isn't subtly weirded out by the dupli-arms.
A niche theme I really dig is the 'eldritch horror support group' angle. Dark Shadow is a sentient quirk with a mind of its own, and Shoji's mutation is... intense. Fics that have them quietly discussing the experience of not-quite-having-a-normal-human-body, the strange perceptions, or the weight of containing something other, they always hit different. Less romantic tension, more profound mutual recognition. Though, gotta say, the romantic ones often use that as a super slow-burn foundation—two people who already get the weirdest parts of each other on a fundamental level.