Aya Tachibana is a sixth-grader who is concerned about her friends, family, schoolwork, and other concerns. She eventually joins the "Tantei Team KZ," a group of four oddball males she met in cram school. There's Kazuomi Wakatake, the glib and attention-getting leader, Takakazu Kuroki, the mysterious "specialist of personal connections," Kazunori Uesugi, the clever and austere math genius Kazunori Uesugi, and Kazuhiko Kozuka, the sweet-hearted social and scientific expert. "Tantei Team KZ" becomes involved in modern-day problems, and even if they fight occasionally, they collaborate by combining each of their abilities and expertise to solve these issues.