TBH can't even think of an actual mainstream series where a cute girl actually ends up with an ugly guy, unless they're 1-bit joke characters not integral to the plot.
Like, show me a single anime starring an ugly guy who somehow has girls interested in him.
Yeah there are non-Chad protagonists but even though they might be short/thin they usually manage to be at least average-looking facially.
Despite anime being full of cope and pure waifus (why I enjoy it) even it has limits in creating situations because they need to at least plausibly allow us to suspend our sense of disbelief.
They don't even have ugly guy protagonists landing ugly girl protagonists. The closest thing to that was probably the 1980s baseball anime Touch where the landwhale QT was chasing that horseface guy interested in the girl the twin bros fought over until he finally woke up to having zero chance and beat the shit out of guys bullying the landwhale.
Even then, he kinda mogs me, and he was a tertiary character.