The Grisaia series may explore its five main heroines in considerable depth over its duration and various routes, but ultimately, the central character to the overall narrative is protagonist Kazami Yuuji.
Yuuji is one of the most distinctive, memorable and unusual visual novel protagonists in the entire medium. Through The Fruit of Grisaia’s exploration of him over the course of the five heroines’ routes, we learn a few details about him and his mysterious past. If you had come to the series completely blind, this would have the effect of gradually shifting your expectations: what might initially appear to be a relatively conventional high school-themed ren’ai (romance) visual novel slowly reveals itself to be much, much more complicated than you might expect.
And then you come to The Labyrinth of Grisaia, whose “Grand Route”, also known as The Cocoon of Caprice, finally gives us some concrete answers about who Yuuji is, why he is the way he is and the circumstances that brought him to Mihama Academy in the first place.