Spiral: Suiri no Kizuna

A high school student named Ayumu is drawn into a mystery after his older brother, a renowned detective, vanished while pursuing the enigma of the "Blade Children." When Ayumu is wrongly identified as a suspect in a school murder, he teams up with Madoka, his sister-in-law and a fellow detective, to prove his innocence. As they investigate the crime, they discover connections to the Blade Children, raising more questions about their identity and purpose.