Ever since MonMusu, the anime community's obsession with monster girls has been near rampant. The sheer insanity of the now-trope generated quite a significant amount of popularity and cash, and additions to the "genre" were sure to follow. That's where we get Demi-chan from, an adaptation of a manga produced on the wave of post-MonMusu (manga) popularity. Thankfully, Demi-chan is a far more reserved and character-focused show than its contemporary, and it helps round out the selection of CGCS offerings for this season. I'll juts get it out of the way now and say that the audio/visual qualities of the show are very typical for the genre: over-abundant focus on character design, very little character motion outside of reaction faces, cutesy art for figure sales, and generic relaxed/happy music. An aesthetic masterpiece Demi-chan is not, but that's not why you'd ever watch this show.
Demi-chan chooses to focus on the high-school life of 3 demihuman girls and their biology teacher Takahashi, who is interested in demihumans as a research subject. A naturally caring person, Takahashi helps these girls with their both simultaneously normal, relatable, yet supernatural problems while also interviewing them for the purposes of his own biological study. Another teacher, a demihuman herself, enters the fold as well, providing a much needed and appropriate romantic interest for Takahashi as well as an adult foil for the 3 demihuman girls to rely on. The "demi" portions of the characters are far more muted than something like MonMusu, with the cast consisting of a vampire, dullahan, snow-woman, and succubus instead of the... more monstrous ones you might have been expecting.
The biggest thing that I can nail on this show is that it's incredibly predictable. It uses its more muted themes of "being different" to convey lessons about growing up, fitting in, self-esteem, etc... It's about exactly what you'd expect from the first couple minutes amidst the typical anime high-school tropes like a teacher-crush and a few other hanging-ons. However, what you might not expect is just how genuine these themes come across, and how the show can hit pretty hard with both the feel-goods and the feels when it wants to. This is due in part to just how geniuine the characters come across on-screen, and you'll really come to empathize with them over time even if you might be able to call out the actual "plot" a few minutes in to the episode. Demi-chan is much more about the characters and their feelings than the ride they may take to get there.
If you like to sit back and relax with one of these cutesy feel-good shows, Demi-chan should be right up your alley. Despite not being anything really new or aesthetically great, it's employed pretty damn well. Fans of the genre will feel right at home, whereas fans of the "genre" might want to check r/hentai instead.