A film that begins like a regular "island" drama, but turns into a murder mystery later on. While that came as somewhat of a surprise to me, by the time the film ended I suspected Midsummer's Equation was part of a larger franchise. I wasn't surprised to find out then that this is a book adaptation (from the Keigo's Galileo series).
The main character is the biggest giveaway. Manabu is a very methodical man, a scientist who believes in truth and facts as the ideal guidance for human choice. He's really the perfect lead for a murder mystery, though that also makes things pretty predictable. With a man like that on the case, you know everything will be neatly wrapped up by the time the film's finished.
The setting's a big plus, performances are on point and the cinematography is well above average, especially for a franchise film like this. The mystery takes up a little too much time though and I would've preferred a bit more island drama (like the water rocket scene), but all in all this was a pretty pleasant watch.