If there was a show titled "A Sister's All You Need," what would you expect it to be about? You might think it would be a sweet story about a loving family consisting of a brother and sister. Now, if I said this was an anime, and you knew better, you might think this was about a sister who has an unhealthy lust for her big brother, insisting that they get married and that he use her in the way he might a true girlfriend and romantic partner. The 2017 anime isn't about that either, but Itsuki, the main character, wishes it were. And that's the problem. Itsuki is a college dropout, but at his young age, also a published and successful light novel author in Japan. Most days, he'll work or hang out in his small apartment, along with friends like Chihiro (who cooks for him), Nayuta (also a talented novelist and youngest among them), Haruto (a novelist focused on his upcoming anime adaptation), and Miyako (a college student). They get along and joke around, passing time in their young-adult lives. Itsuki, however, has a unchecked "little-sister" complex, which comes across in all of his published work. He isn't ashamed of it either; it's his trademark motif. He even has a deep knowledge of anime and erotic visual novels that use the trope (most of which proudly sits on his shelf as reference material). If only he had a real little sister, to wake him up in the morning and whine when he's out for too long... alas, the man can dream through his creative passion.It's not just the lead character either: seemingly all of his friends have similar unhealthy fetishes. Nayuta has a hardcore crush on Itsuki, constantly asking to marry (or at least get physical with) him. Haruto also has a unhealthy amount of erotic-anime material in his home. Elsewhere in Itsuki's life, he works with a young illustrator who insists on seeing naked bodies to inspire the art he draws, and later a "tax accountant" with a sadistic-fetish side comes in. Miyako and Chihiro seem to be the only ones that are "normal" relative to everyone else.In short, "A Sister's All You Need" might be the most disgustingly perverted mainstream anime I've ever watched. Entirely because of these fetishes held by each character. The age of each character is also problematic to the premise (Nayuta is supposed to be 18, under Japan's drinking age of 20, but being able to blurt out "F*** my face" when being told she's "underage" made me shudder). Funimation's English dub is liberal with the slang, not hesitating to swear or use the "F-" word, or to describe in detail pop-culture references to other fanservice work. All the while, the audience slowly learns that... Chihiro, the silent character cooking and looking after Itsuki, his in fact his little sister? He HAS A REAL LITTLE SISTER?! The dynamic there isn't at all like one might expect from Itsuki and his "appreciation" for fanservice anime, but it's confusing when it's first hinted at, and kept in the background until much later (and even then, it's never fully addressed in the anime by the end).It's not like "All You Need" is the first or only anime to push the envelope however. In fact, it relies on dozens of existing work for its references and jokes. One could argue that it's a commentary on how far gone Japanese anime and manga have become, slowly making fetishes mainstream. Or a commentary on the viewer, who would be willing to overlook such gross behavior and interests. 
And indeed, I did overlook it a little. And beyond the fetish stuff... "All You Need" is actually pretty good as a slice-of-life comedy-drama. I swear, I'm being serious!Yes, the fact that everyone is a "manga" or "light novel" writer in this story subconciously puts its target audience in a fullfillment fantasy. But I enjoyed the characters (beyond their fetishes), their dynamic with each other, and some of the humor, such as Itsuki's editor constantly searching him out to meet his deadline, or random day-trips across Japan. It reminded me a lot of "The Pet Girl of Sakurasou," an anime I actually quite admire, even when I knew it was manufactured to a target audience like me. There are some romantic dilemmas, and some drama with novel popularity and adaptations, helping keep the viewer invested in the second half of the season. However, several plot developments aren't properly addressed by the final episode, so it's frustrating not to have a second season... or even just one more episode to tie everything up. Even without a real story or plot to drive anything, I enjoyed watching... even though I had to overlook the characters' behavior, like not reporting to the police when a close friend was suspect of something... You can tell I'm conflicted here, and I wish that the show had edited out all the gross material, even if it means lacking much of an identity of its own. The production of "All You Need" is competent. Character designs are definitely distinct and feel lived-in, but not always good or sensible (why is a male illustrator wearing a dress all the time, and never addressed about it?). Promotional materials overlay the characters on real-life photos of Japan, but no such ambitious shots are used in the show. Animation is fine, not notable but not noticably bad either. There are a limited number of fanservice scenes, but no nudity, and the quality of these scenes show where the money really went (it's surprising they didn't push that aspect harder here; the verbal jokes alone already push the show to be rated "R"). Some might be concerned that Funimation's English dub is too liberal, but their freedom allowed the acting to feel more natural, and allowed some of the jokes to land better. The music, especially the opening and ending themes, are also way better than they have any right to be."A Sister's All You Need" is actually pretty good, as far as this genre (young people working in creative industry and hanging out with each other) is concerned. But the crude and vulgar humor should make one stop and pause. For most people, it's gross enough to be easy to pass on, and easy to recommend avoiding. And if you think it's funny, and like the show, you might want to double-check yourself and what you have on your own home shelf. Despite it all, I cautiously admit that I think I liked the series... and already feel gross in admitting that, and will now question what I watch more closely. A quick scan of online reviews suggest the show is actually well liked too... maybe only "men of culture" could truly understand it.