If you like mysteries, you absolutely must play The Sekimeiya

This is a criminally underplayed visual novel (according to the ending stats, fewer than 500 full completions - at least registered online by Steam) and I think it deserves more exposure.

Do you like VNs like Higurashi, Umineko, Ever17, Remember11, or even the Zero Escape trilogy? You should definitely consider giving this one a try.

The mystery is absolutely superb and the setting enthralling - there's a constant great tension, and the plot is very well thought out with no plotholes or Deus Ex Machinae. If you enjoy the feeling of being thoroughly overwhelmed with a complex puzzle that steadily becomes less opaque, you will definitely enjoy your time here.

It's not a perfect VN, but it's relatively concise (30-40 hours total) and left me craving more. I would recommend it in the highest possible terms if you're a fan of the mystery genre.

That being said, as downsides, it's unlikely to appeal to you unless that is your genre of choice; while character dynamics are very fun, there's very little slice-of-life and the main focus is definitely the mystery itself.