Mystereet ~Fukagyaku Sekai no Tantei Shinshi~

Become Yasogami Kaoru, the youngest class A detective in IDLA, an international detective organization, and solve difficult cases that baffle veteran policemen. Although the game is split into episodes, the plot lines are interconnected and the web of relationships are so intricate that it is a real challenge to find the culprit and his or her motives.

The game is split into four episodes and a prologue. The prologue demonstrates the prowess of the youngest class A detective in action as he solves a murder case on a cruise ship. The main storyline starts at the first episode where Kaoru accepts a case from IDLA's Director Connor, to locate the legendary detective Agyou Sohma who disappeared. To solve the case, Kaoru masqueraded as a class D detective and entered Sohma's Shiawase Detective Agency. To make matters even more complicated, Shiawase Detective Agency has a accepted a case from a Mrs. Toudou to catch the mysterious thief Sapphire.

After solving Mrs. Toudou case, Kaoru, still in disguise, is given another case to solve in episode two, he is to find out the truth behind the mysterious fire that burnt people to death in the local church, and at the same time, figure out the cryptic message the pastor left before his own death. In episode three, Kaoru receives a challenge from another class A detective, to find out a murderer amongst five hypnotized persons.

The grand final of this game lies in the last episode. Class A detectives from all over the world are invited to Baron Kazamatsuri's deserted mansion to solve a foretold murder case. Sohma Agioh name is in the list and old foes like the mysterious bandit Sapphire shows up. Can Kaoru solve, or even prevent the murder case and find Agyou Sohma in this grand finale?