In the meantime, guess what? The harem lead gets to maintain a happy non-sex driven relationship with the girl who he truly loves and get to live a happily ever after ending because that's how a relationship should be: with the one person you truly love forever and ever.
Fucking faggots, man up and stop thinking about sex. See that math textbook on the floor next to you? Yeah that, pick that up and teach yourself what a fucking quadratic equation and do some more algebra. That's what you should be doing, instead of obsessing about how Nagasumi, Keitarou or Tsukune didn't knock up their respective harems. In the end, they got beautiful devoted wives who'll be there for them until the day they die happily in a lodge by the sea, a special person you won't even be able to get to meet before you die at this rate.