According to Comic Natalie, a new OVA
of Nurarihyon no Mago
was announced to be released on March 4, 2013. It will be bundled with the final volume of the comic book. The OVA will reveal the story of how young Nurarihyon established Nura Clan.
Key visual of the OVA
The 24th volume of the comic book was also announced
to carry an OVA. It will be released on December 4th.
Source: Comic Natalie