Jiraiya/Naruto romance stories usually end up as extreme age-gap power fantasies with a heavy dose of mentor worship. You'll see a lot of 'Naruto seeking comfort' arcs after a betrayal by Konoha or Team 7, with Jiraiya stepping in as the one who always believed in him. The dynamic shifts from grandfatherly to romantic with this jarring, often poorly explained, turn. Then there's the whole 'training trip' reimagined as a slow-burn journey across the world, where they're forced into close quarters. It becomes less about mastering rasengan and more about shared ramen and late-night talks by campfires. I've also noticed a subset of fics that frame it as a forbidden love, playing up the taboo of a Hokage candidate and his legendary Sannin mentor, with Tsunade or the Council as antagonists. Honestly, most of these plots rely on bending Jiraiya's canonical character past the breaking point—he's either stripped of all his pervy traits to become this perfect, patient lover, or those traits are exaggerated into a weirdly predatory vibe that makes me click away fast. The appeal seems rooted in that deep, unconditional support Jiraiya showed in canon, stretched into a romantic ideal.
You also get a surprising number of time-travel plots where an older Naruto goes back and falls for a younger Jiraiya, which flips the power dynamic on its head. Those can be interesting if they explore the guilt and weirdness of it, but they often just use it as a setup for smut. I tried reading a few, but the tone is never consistent—it wobbles between tragic romance and pure wish-fulfillment.