Romulan vessel in 2266, he paused a moment to check her out as she sat down before returning his attention to the battle. While under the effects of polywater intoxication that same year, he made his way to the bridge armed with a sword and grinned when he saw Uhura, declaring her a "fair maiden" (despite her protest that she was neither) and promising to "protect" her. Nothing apparently ever came of his romantic interest in her, but they did eventually become friends. Uhura was willing to keep his secret when he didn't want to admit to being lost while on a hiking trip in 2287. (TOS: "Balance of Terror", "The Naked Time"; Star Trek V: The Final Frontier)Long before I shipped Uhura & Spock, I was quite fascinated with the notion of Uhura & Sulu. Needless to say, such fiction was rare, and while there may be a few more pieces now, it's still not a common pairing. Either way, I think fans of these two have plenty to work with.
mirror universe, however, Sulu's crush on Uhura was much more blatant, and very dangerous for the Uhura of this universe when she found herself trapped there. Mirror-Sulu made no secret of his attraction; he openly propositioned her on the bridge when Kirk and Spock were absent, insisting that she would "change her mind" about him if she gave him a chance. Uhura later took advantage of mirror Sulu's lust when she needed to distract him for a moment, briefly pretending to return his interest and then slapping him in the face and drawing a knife once the moment had passed. (TOS: "Mirror, Mirror")"
Furthermore, I think this is great opportunity to bring Sulu into the forefront. I always admired this character, and when I first learned John Cho was going to play him in the Reboot, it was all I needed to know. I can't think of a more perfect time and place than the Narrative to explore this pairing. It's like exploring Blasian love in retro-nerd style.