Kiyotaka Narumi

Ayumu's older brother, who is perfect at everything in the eyes of Ayumu. He became a world-class pianist after the age of ten and then an unimaginable world-class detective at twenty. He married Madoka - but left a year after they married. He is also the real reason why Ayumu always doubts himself, who is constantly comparing himself to him. Kiyotaka left one day after he was researching the mysterious case of the Blade Children. Many assume he is now dead. Ayumu discovers that he is not, after hearing that he has been associated with the Blade Children.

(Source: Wikipedia)