Honestly, the fanfic versions of that scene are way more tense than canon ever managed. Canon was all about misunderstandings and slapstick, but fics dig into what's bubbling underneath: the sheer relief of finally stopping the charade. I've seen writers play it as this desperate, giddy release, both of them laughing and crying because the fake-dating pressure cooker finally blew its lid. Other times it's pure anger-fueled passion—all that built-up frustration from three years of 'Nisekoi' nonsense exploding into a kiss that's more collision than romance. What gets me are the quieter ones, though. The fics where it happens after some minor crisis and it's not dramatic at all, just this soft, inevitable click, like a lock turning. They capture the weird intimacy of having shared a life, even a fake one, for so long. The emotion isn't just 'love,' it's exhaustion, familiarity, and a shared history that's real even if the relationship premise wasn't.
I think a lot of writers use it to fix the manga's pacing, too. The original stretched things so thin that by the end, some readers just felt numb. Fanfiction condenses that simmering tension into a single, cathartic moment. It's less about the kiss itself and more about the emotional permission slip the writers give themselves—and the characters—to finally be honest. You can feel the authorial satisfaction in the prose, like they're saying, 'There, was that so hard?' It's a reward for the audience's patience as much as the characters' journey.