When Shimizu Takashi releases a new movie, I will certainly watch is as soon as possible, and I did not regret it.
The beginning is mysterious and cozy during the first 15 minutes. One of the main characters is an old detective, who is hired by the manager of a boy band. The boys don't look like actors, but made a striking impression, especially one called Sekiguchi Mandy. When they came together, I was surprised by how many characters there are. But then I thought that it is probably just so that they can get spooked one by one.
It was only later that I learned that the boys are actually from a real group called Generations from Exile Tribe. Since they are real people, one can suspect that they will not be painted in a bad light. There are of course other horror movies with idols playing themselves, like Shirome by Shiraishi Kouji, which turned out interesting. Incidentally, the actress Hayami Akari playing the manager in Sana is a former idol and was in Shirome.
The boys are acting well for not being actors. I think fans might enjoy seeing their idols caught in a mystery scenario.
The acting performance of the antagonist is also good, with a few nice scenes apart from the scares.
Shimizu Takashi has a habit of showing off his antagonists early and often, just to scare the characters without anything serious happening. Moreover, it is often done with exaggerated antics.
Even if I didn't know the director, I would have guessed it easily, because the film very much has his style and lore. Especially one scene was like taken directly form Ju-on/The Grudge (by the same director). Not exactly element by element, but it was like watching Ju-on for a while.
But another scene was worse. One of the most stupid scenes I have ever seen in a serious movie. I would not even be able to describe it without taking a screenshot, because it barely obeys the laws of physics.
It doesn't end there, because there is a third stupid scene, involving a door that has fallen down on the floor, and is also closed at the same time. Let's call it Schrödinger's door. I am thinking about taking a screenshot, drawing arrows, and writing a quantum wave equation to explain it.
Since much is centered around a song, it is inevitable to compare it to the ringtone in One Missed Call by Miike Takashi. The history of the song in Sana is interesting, but the song itself is neither creepy nor catchy.
A critical stat for a horror movie is of course how scary it is. I seldom feel fear in horror movies, it was mostly cringe in this one, but I can make an educated guess. Since its scares are similar to Ju-on, and Ju-on is considered one of the scariest, Sana might also be considered scary, theoretically.
There are a few irritating aspects, but that is not always fatal. Worse is that it feels boring and not very fascinating, which is more fatal.