I love everything about this game. Good writing, funny dialogue and situations, great romantic scenes, interesting plot, and every girl is unique & extremely loveable. How can a 1 man team put many professional studios to shame?
Selebus has briefly mentioned having worked on writing projects before, specifically while talking about how he keeps from burning out in this project, so I would say previous experience comes into play here and probably a bit of raw talent as well.
He also sticks to his vision no matter what, unlike some other devs who let the players drive development, sometimes to the point of completely derailing development from where it should be going even with some player requests on the side, a great example being Lilith's Throne.
We do get some input here, of course, and some in game bonuses for those paying, but development is basically all his plan. The most we get is what new character gets added when and that only happens occasionally and is really only something for him to consider, not a definitive decision to my knowledge, thankfully. While I would love to see all the characters he has planned ASAP, I don't want that to come at the cost of development quality.