itch.io

I'm getting it, and can screenshot if needed; but it's the entire "Congratulations, you've completed every character's main story" through "But you don't have to at all ... Thank you so much!" series of four messages.
I'm getting it on every load in to the lobby, or my room; as well as clicking on the stairwell from the first floor; and across multiple in-game days.
I downloaded v0.19 from the first link above, un-zipped it, and played directly off of that... It's the same way I've done all updates to-date.

I'm finding the same with Nia too!

Am I blind? Where is "the big red button"? The closest I'm seeing the orange Patreon button, and that didn't do it. Love the game BTW, can't wait for the next update!

No, and I doubt it will be added... Maybe they'll do a version where you play as the Head Mistress at the boys school; but I doubt it.