Crimson

In this universe, there are four distinct worlds: Meikai, the central hub of the universe; Ninkai, the world inhabited by humans; Youkai, where shape-shifting monsters reside; and Shintenkai, the realm of the Celestials. Shiba Yukinari is one of the rare individuals born with both Youkai and Celestial heritage. By day, he operates as a detective, but he also undertakes the task of exterminating youkai. As he gathers 'cores,' which are the sources of a youkai's power, he encounters Riifei, who demands that Yukinari surrender his own 'core'... Volume 1: Crimson Volume 2: Crimson Crown Volume 3: Crimson Chaos (Source: MU)