Nurarihyon no Mago: Sennen Makyou

Synopsis

Two mysterious men arrive in Ukiyoe Town. It is revealed that they are Ryuji and Mamiru Keikain, Yura's older brother and childhood friend who have come to find Yura. During the search, they encounter Aotabo and defeat him. Meanwhile, the Kiyojuji Paranormal Patrol is on another yōkai search, but decide to search for Yura, who has not been attending school recently. Rikuo finds her training in an abandoned place. Moments later, Ryuji appears and realizes that Rikuo is a yōkai. At first, Yura doesn't believe her brother and tries to protect Rikuo but she is defeated. As night falls, Rikuo transforms into his "night" form.

(Source: Wikipedia)