honestly, finding stories that do the dynamic justice is harder than you'd think. A lot of them jump straight to the romance without any of the fascinating philosophical groundwork, which misses the point entirely.
My absolute top recommendation is 'Two Legends, One Purpose' on AO3. It's a sci-fi epic where Mewtwo, after the events of the first movie, encounters a Lucario who's the last of his kind from some ancient war. Their bond isn't romantic at first; it's more of a grudging partnership that morphs into this profound understanding of being singular, powerful beings in a world that either fears or wants to use them. The writing gets into the ethics of artificial life versus natural aura-guardians in a way that feels really thoughtful.
Another solid one is 'Aura's Shadow' on FanFiction.net. This author focuses on the telepathy angle, with Lucario being one of the few beings whose mind Mewtwo can't fully breach because of aura. That resistance sparks Mewtwo's interest in a way that feels very in-character—less about attraction and more about intellectual challenge. Their conversations are the highlight, full of tension and this slow-burn respect that eventually tips into something deeper.
I'd steer clear of the super-short one-shots that are just fluff or pure smut, unless that's specifically what you're after. The pair really needs space to breathe and develop, so look for multi-chapter fics where their power dynamic and alienation from their own species are central themes. The best ones treat them as forces of nature learning to coexist, then connect.