The Afterglow of Grisaia takes the form of a side story to The Labyrinth of Grisaia. The game is a story-driven visual novel with serious overtones.
The Labyrinth of Grisaia shed some light on Kazami Yuuji's past, offering a deeper look at events stretching as far back as his birth. This story, however, concerns Yuuji's experiences with Kusakabe Asako, the CIRS agent who rescued him at a young age from a terrorist organization.
It is recommended that you play this game only after having played The Labyrinth of Grisaia.