Dozens of goldfish were smuggled into the pool at night at the school . Who did it and why? The "Deduction Trio" of the 4th grade class - Tsujido Tenma, Yuzuki Riku, and Kamiyama Misuzu - are tasked by their homeroom teacher, Ms. Mariko, to take action! Can you take on the challenge of the great detective Tsujido Tenma? What is the truth of the matter? Collect the clues in the book and start your exciting deduction!