Wealthy heiress Reiko Hosho leads a double life as a novice detective. One day, an incident erupts at a birthday party she attends with friends from her college days. The victim is one of her old classmates, and Reiko's friends are labeled as suspects for matching the attacker's description. Stirring in confusion with only 20 minutes to solve the case, a man suddenly appears to reveal the culprit.

Mystery butler Kageyama concocts a peculiar plan to catch the criminal lurking in a luxury hotel, after which Reiko and her friends realize the hidden complexity of their own emotions. Reiko then tackles the murder case of a real estate tycoon. Each of the victim's relatives harbor suspicious motives to kill, but a single photograph proves essential in accelerating this perplexing investigation.

While investigating the murder of a real estate tycoon, Reiko examines an erased dying message, a bloody trophy, and a cord yanked from the curtains. Without proof, however, she reaches a dead end...until savage butler Kageyama emerges to solve the mystery. Reiko and Kyoichiro think outside the box to trap the murderer, peek inside the victim's mindset, and end a chain of events fueled by revenge.

With Kageyama as her chauffeur, Reiko and her friends visit a crowded summer festival, where a cracked smartphone is discovered. Its owner was poisoned in his apartment, and he died wearing nothing but briefs. Three women the victim dated simultaneously on a matching app fail to match the height of a suspect seen exiting his residence, which leaves Reiko puzzled at the true culprit's identity.

Women of differing heights are spotted at the crime scene. Kageyama suspects that elevator shoes disguised the murderer's appearance. After learning that the victim had scammed several women via dating apps, Reiko inches closer to the truth. Later, a delivery man is found dead with an item belonging to his favorite VTuber, and it's discovered that the two even frequented the same hospital.

After a delivery man falls to his death, Reiko and Kyoichiro investigate his connection to popular VTuber "Kuru Kuru-Chan," who is blamed for the murder by fans online. Kageyama assists in analyzing a mystery figure planting bugs, untouched food deliveries, and hints to the true culprit left at the crime scene. The victim leaves a note reading, "I've had enough of this world," but in what context?

A famous painter is stabbed in his own studio, pointing to his masterpiece wall painting "Sleeping Beauty" just before dying. Suspects include his art-jacking son, his second wife, and an art magazine writer with whom he supposedly had an affair. Reiko and Kyoichiro investigate how the killer escaped a locked studio, eventually learning of the victim's connection to a certain "Appraisal Queen."