High School DxD, Vol. 12 (light novel)

A swarm of giant monsters has appeared and threatens to destroy the underworld, yet Issei...is nowhere to be found. He-s gone, and the rest of the Gremory Familia is in pieces without him. I, Yuuto Kiba, can only push forward in the face of death. Issei, please lend me just a little bit of your courage. I-m going to need it.?