Spiral - Suiri no KizunaSpiral: Bonds of Reasoning, Spiral ~ Lines of Reasoning, Spiral ~ Suiri no Kizuna

Two years ago, the famous detective Narumi Kiyotaka disappeared, leaving behind only the words, "I am pursuing the mystery of the Blade Children." Now, his younger brother Ayumu is accused of murdering a fellow student, and begins to discover people with connections to the Blade Children all around him. The Blade Children were born cursed, and Ayumu may be the only key to saving them, but first they want to test him, by trying to kill him with everything they've got. All the while, it seems that Kiyotaka is manipulating events for his own unknown purposes. - From AnimeNewsNetwork Ongoing