The Flowers of Evil continues to progress in volume 5. As this volume begins, the school season is winding down and summer break is approaching. Saeki is confiding in her friend Kinoshita, who has been developing as a character in her own right over the latest developments in the story. We gain some insight into possible ways Kinoshita could effect the story in future volumes. Nakamura and Kasuga start laying out a grander scheme plan on the unsuspecting countryside. However, Saeki and Kinoshita may interfere with their laid out plan.
A solid chunk of the volume provides us with some further insight to the characters. Nakamura and Kasuga continue to deepen their relationship, almost becoming one in terms of mental state. Kinoshita and Saeki each have their own ideas for how to handle the current situation, but does Saeki have her stance because she still cares for Kasuga?
The final third of the book brings Saeki, Nakamura and Kasuga all together again and it involves the plan Nakamura and Kasuga had. All of the events of the previous volumes come to a head at the end of volume 5 in a very emotional and destructive scene. The event will no doubt effect each of the characters in a different way in the next volume.