An OVA is scheduled for volume 18 (final) Limited Edition.
Edit:
The bundle with the "Ijin-tachi to no Haru" original video anime will ship on March 25, 2015.
There is an OVA trailer. To watch it see where it says
18巻OVA PV公開!! here:
http://dash.shueisha.co.jp/papakiki_2014/