You know, compared to characters in some other series, Koharu really does look like her a parents to a fairly reasonable extent. She doesn't look too much like either of them to where they might seem like older versions of her, but at the same time she doesn't look so different that you question if they're even related.
Her hair, especially, really does kind of look like a mix of both of her parents. Like it's (a messier version of) the volume and shape of her mom's hair but with the shade and texture of her dad's, which results in something reminiscent of both yet still distinct from them.
It's pretty neat, I think.