Opening:
Well yeah, after all it's the first thing that you see and hear from the anime (aside from one scene), so why not begin with this. I have to say, the opening is rather clean and enjoyable, so I didn't skip it much (I usually skip anime openings once I've heard them once or twice). The drumline in particular is very good. On the other hand, the ending is okay but not great.
Visuals:
While not astounding, the colors and visuals are pretty and contribute to the cuteness of the show. Mostly pastel colors and soft shading create a warm atmosphere, letting the viewer get comfortable and follow the story. No unbelievable hair color or haircut (except Hikari's, but it's explained anyway) help by placing the show in a semi-realistic setting.
Characters:
As with any slice-of-life show, the characters are kinda normal (except that, you know, some of them are actually monster girls). Imo, the show manages to paint them as realistic characters by highlighting both their flaws and their strengths as demis and humans, which is really important when you consider the premise and is crucial to make them relatable. The main trio follows a rather classic genki girl/ladylike girl/quiet girl, and the fourth demi is the MC's main love interest, so it's not like they were very original here. Yuki does open up a bit later on though, and her personality becomes more interesting. The MC itself is a bit more unique in that he doesn't fall into the classic SoL MC category: he's intelligent, kind but level-headed, doesn't end up in weird situations defying every law of physics (looking at you, Yuuki Rito and Kimihito Kurusu) and is actually much more fleshed out than most main characters in slice-of-life. The last episodes in particular complexify his already decent character, which is a relief. There are not many secondary characters and many of them do not have much of an impact until late in the show, but said impact in the last episodes is sweet, so I'll give them a pass.
Story:
The story isn't very present as it is a slice-of-life and thus not as reliant on plot than more action-oriented animes, but there is still a sense of progression, which is satisfying for the viewer. Now, here's the catch: from ep 1 to 9, you'll be seeing an average (but nice) comedy slice-of-life anime. However, ep 10 begins to raise important questions and thickens the plot, while ep 11 and 12 just turn up the heartwarming button up to eleven, maybe twelve. Actually, these two episodes alone are probably more than enough to make the show worth a shot. The relationship between the main characters (and even with secondary characters!) becomes outright adorable and you'll end up regretting that it cuts short like this. Definitely a feel-good anime, but it does raise some philosophical questions.
Humor:
I was expecting more humor from this, so it's a bit of a surprise, but the show is more adorable than funny. However, the jokes and running gags in Demi-chan are spot-on (imo) and made me laugh. Hikari's antics never get old, Kyoko's appearances alternate between funny and d'awww, and Yuki of all characters becomes an unexpected comic relief at times, not to mention every flirty interaction between the MC and his succubus colleague (the guy has some buddhist levels of self-control btw).
Plotholes:
Sadly, this anime is also subject to plotholes, which are probably explained in the original support but is left out here. Among them:
- Really, who is Kurtz, the anti-succubus police agent, and what's his power? He just appears out of nowhere and disappears as fast, with no explanation given whatsoever...
- What does Takahashi's dream about being attacked by a vampire brings to the show? Is that foreshadowing or is it just to introduce his whole "nocturnal animals have their own eye properties" speech?
- What did they do to prevent heat from weakening them? It's probably a sequel hook, but still...