Let's talk Gakupo and Luka specifically. Their dynamic, at least in the fanon I've read, gets interesting because you've got two very distinct vocaloid personalities—one steeped in traditional Japanese aesthetics, the other this sleek, futuristic pop idol. The conflict rarely feels like simple romantic squabbles. It's more about dissonant worlds colliding. Gakupo's samurai code, his sense of honor and maybe even a touch of melancholy from older songs, clashes with Luka's more cosmopolitan, sometimes ambiguously cool demeanor.
I've seen fics where this plays out as a literal culture clash; she wants to move forward, he's anchored in the past. Other writers dig into the metaphysical—two beings created for song, exploring what 'emotion' even means for them. Are they simulating it, or is it real? That internal conflict, the questioning of their own authenticity, gets layered onto their interactions. It's less 'will they or won't they' and more 'can they even understand each other?' which makes the moments of connection, when they happen, feel hard-won and strangely poignant.
The best ones I've found don't just paste a human drama onto them; they use their core concepts as the engine for the emotional tension.