An unexplained event sometime before the anime starts resulted in people seeing aberrant creatures, known as "Phantoms". These phantoms range from harmless inanimate objects which have manifested themselves into personalities, to dangerous creatures capable of murdering dozens of people.
Given the potential danger these phantoms can pose, you would think that there would be a special force set up designed to banish these phantoms as soon as they appear - after all, having scores of people murdered by rampaging giant monsters is not exactly something desirable.
Instead, the story follows a group of high school students (it's always high school students..) who are training their powers in order to combat the phantoms. From right here you can see something doesn't add up - why would the defeat and capture of dangerous mythical creatures be left to the hands of emotional, untrained teenagers and kids? This particular side is never addressed. It's just seen as the norm for non-adults to take care of everything, whilst the teachers and other grown-ups just stand by at the sidelines, doing nothing but watching events unfold.
There's no real plot to speak of. Each episode starts up with Haruhiko breaking the 4th wall, telling the viewer what the episode is going to focus on and giving some trivia pertinent to the events about to unfold. It is entirely episodic, too. Each episode focuses on a different character - one episode about Mai, one episode about Reina, one episode about Koito; so on and so forth. There isn't any progression.
The characters themselves don't really have any defining personalities. Haruhiko is just the regular MC. He occasionally helps out. He's a nice guy, lending aid to people whilst being beaten up and slapped by the members of his harem when the tired old tropes and clichés appear, such as him tripping into someone's panties.
Mai is one of the two primary focuses of the fanservice; she has to rub her tits and other parts of her body whilst chanting in order to activate her powers.
Ruru is a Phantom who exists purely for fanservice. She does nothing else. For instance, in one scene Mai and Haruhiko are talking. Rather than focus on the talk, the camera zooms in on Ruru and we simply watch her doing leg exercises, whilst the conversation carries on in the background.
Koito, Kurumi and Reina play the role of the kuudere, the loli and the shy one, respectively.
All of the characters get an equal amount of screentime, and contribute an equal amount to the events that unfold. Each are given an episode in the spotlight which focuses on their problems and their past.
The art and animation is the absolute high point for the series. Say whatever you will about the rest of this anime; the art cannot be faulted. Simply put, it is gorgeous. Even without the fanservice, it is nothing short of pure eye candy. The art is crisp, and the colours vivid. It makes it a pleasure to watch, even when one finds themselves uninterested in what's actually happening. The animation is top-notch, too. This is especially apparent where the phantoms are concerned. The effects used on them - such as the particles emanating from some of them, and the way they flicker as they move around - look awesome. You can tell a lot of effort has been put into it - nothing less expected of KyoAni.
It is a shame, then, that it is only the art and animation that has had a lot of effort put into it. Each episode consists merely of tropes, clichés and all the regular things associated with fantasy highschool harem anime. If you're a fan of this particular genre, then you will probably enjoy Musaigen no Phantom World. It brings everything we've seen before, but with the art and animation cranked into overdrive. I will mention that the fanservice is reduced in the quantity in the later episodes. It is not nearly as prevalent as it was at the beginning.
But if you're tired of the same old, then avoid this. There's nothing new about this. There's no particular reason to prioritise watching this over any other highschool harem.
I gave this a 4/10 overall. There was no real reason for me to feel invested or interested. If not for the amazing art I would have rated this lower. It isn't bad; it is merely uninspired. If nothing else, watching this was made easier when I stopped thinking about what was happening and merely enjoying the aesthetics.
