Explicit: Syaoran X Sakura Implicit: Fay X Kurogane; Clow X Yuko Go figure.
Also side-character romances in practically every world they visit. I'll just remind you that it's a shounen manga, though, so don't expect sappy love stories.
________________ ABOUT ME 1. 10,000 chapters and counting. (...Otaku alert!) 2. I love Comedy/Romance/School Life (as you probably can tell!), especially when they're all together. 3. I welcome spiffy debate but I don't do quarreling (or forum trolling).