Anyone who watched and enjoyed the previous two series will go into this knowing what to expect, and shouldn't be too disappointed with this hour-long OVA. The fanservice is as prevalent as ever, and there is some after each non-ecchi portion.
As the light novel series is now concluded it is unlikely anything more will be animated. So how does this serve to wrap up the series? Mostly good, partly disappointing. A plot is set in motion right at the very beginning, and is... not resolved at all by the end. Instead of the final confrontation built up over the hour, it ends with the group simply leaving the house to face it. A rather disappointing end given that we probably will not see it at all now, made doubly so given that it could have potentially been included without the pointless Hasegawa addition. With that said, harem fans will rejoice at the end.
Every surviving character (with the exception of Basara's father) shows up in some capacity outside of flashbacks. Not all of them speak, and some that do feel as if they were shoehorned in just to make an appearance (looking at you, vampire kid). Music was generally good, as was the animation quality and sound effects, and the actual characters were as dynamic in personality as ever.
Overall a mostly good end, with some disappointments at what was and was not included.
Its the closest thing to a hentia that you will see. Like all OVA its just full of fan service, plain and simple dont watch it for the story because there is not one its just a collection of random thoughts from the first and second season of the anime.
Like with the entire series, you're watching this wrong if you watched it censored. It's a show where I have to say, "I can't believe this isn't labeled as hentai!"
This becomes increasingly apparent as you start to see Chisato and Basara forming a romantic relationship. If you read the LN (I haven't, I've completely dropped the series cause even though the plot might be nice, there isn't any substance, just sex) or checked Fandom she's apparently his first cousin once removed, and she is waaaay older than him too. Here's the thing though. Since she is technically family, and she is also way older than him, and he isn't even an adult yet... You can see where this is going right?
So here is what happens. During part of the OVA, Basara and Chisato are having a romantic moment, and... Am I even allowed to mention what happened? Just watch it, I won't spoil it for you.
So here's my warning, and start debating whether Boku no Pico or Testament of New Sister Devil is worse.