Today, Animate announced a Joint Event of Oreshura and Haiyore! Nyaruko-san W. However, a few hours after the announcement, it was removed from the Animate site. The article that was also posted at NicoNico but was removed as well. According to the article previously available on NicoNico, Yukari Tamura, who is in charge of the ending theme and is also the seiyuu of Masuzu Natsukawa, confirmed her participation in the event.
UPDATE: Both official twitter accounts for both series unveiled their collab site: http://nyarushura.com/
Via: Animate