I wonder if the girls can bear a child? 'cause it is the only thing left these girls will hound Haruto for
This is
really not the kind of thing I'd normally think about but... probably? They effectively run on imagination/belief. If I'm understanding how they work correctly, if they truly want to and believe they can get pregnant, then they... probably can? If it came to "doing the deed", they have Bellnoa's mini spell or Kusabi's ability to move them to a world where they're the same size as a human. If their canons actually matter and core aspects of their character can't be changed then I'd assume only Nona would be sterile, since in her canon she's an Android. All the others are human to some degree.
Also we know from the Boba Tea chapter they can actualise crafted objects into real equivalents. Haruto could make a paper-craft thing that's supposed to be a tub of his own semen and the moment one of them touched it, it would turn into a real scaled-to-them tub of Haruto's Semen, and then they could IVF with it or whatever.
And failing
that, there's... whatever the dream girl's name is, Yumeka? She effectively has the power to rewrite reality, so she could just decide "okay, Overdrive girls can get pregnant from humans" or "All of Haruto's OD Girls are now pregnant with Haruto's children" and that would become reality.
Between the power of the Shards of Galatea to actualise things touched by characters made from it, and the ability to create a Godlike OD girl from it that could change reality to her own will, even if OD girls can't get pregnant by default, they could be changed to be able to, so it's kind of a moot point.
Probably not with getting them all pregnant, but if this series ever ends with a closed ending, it will probably end with one (probably Nona) or all of the OD girls getting actualised into regular real humans but losing all their fictional character traits (like Bellnoa's magic) once they realise the effective god-tier power the Shard of Galatea enables.