I understand adding new characters but you're missing the point. You're making out with Judith after you ask her to take off her pants, She says I don't feel comfortable yet. Yet. That's many many updates ago. Unfinished. Cassie, she gives you a handjob or sex with or without a condom. You can only choose handjob. She's another one that goes way back. Unfinished. Mrs Bissette flirts with you (offers reward for A's) but can't do anything without Version 3 of the French book. Again very old story but... Unfinished. Roxxy is DC's avatar but it took Forever just to get the shower scene. Thank god for the shower scene! Mia. People were getting really pissed off because he kept putting off working on Mia's story. Her story is super old too.
All I'm saying is add new characters But complete the really old stories first or at the same time.
Different developers in gaming markets handle this very differently.
You introduce a character to see them come up and interact with the cast. Yes, Cassie is unfinished. So is Rhonda, gym teacher, and quite a few others. But you make different characters to appeal to different things.
Coming back to them as you introduce new concepts and make them believable helps immensely.
Also, Mia's story isn't really hers. It's Helen's. He needs to add dating which would flesh out Mia and quite a few other things.
As it stands, 15 MIGHT finish that French book thing along with leave new breadcrumbs to new stuff that was hinted at in stream.
Basically, I see the characters as being introduced to garner interest. Bear in mind that this is also a VN that's being made while forming a team, catering to criticism, and trying to stay on a platform hostile to it. (Patreon)
That's the struggle of being a developer.