Ayumi Narumi (voiced by Kenichi Suzumura), a freshman at Tsukio Academy, has a very high IQ and meticulous reasoning ability, but even so, he has always lived in the shadow of his brother Kiyoshi Narumi (voiced by Kazuhiko Inoue) when he was a child. What he didn't expect was that one day two years ago, his brother mysteriously disappeared after leaving a message about the "cursed child". Ayumi Narumi has always been worried about his brother's disappearance. He wants to know the whereabouts of his brother whom he has always admired, and also wants to find out what the so-called "cursed child" and "unknown truth" that his brother has been obsessed with studying are. Ayumi Narumi met his senior schoolmate Hinano Yuzaki (voiced by Masumi Asano), whose huge intelligence network on campus facilitated Ayumi Narumi's tracking. As the investigation progresses, a truth that is enough to subvert Ayumi Narumi's world gradually surfaced. The animation is adapted from the manga of the same name by cartoonist Kyo Shirohira, which has accumulated huge popularity among readers for its relaxed campus style and rigorous reasoning.