Issei SOS is the thirteenth novel of the High School DxD series. It is the first novel of the Legend of Oppai Dragon and his Lively Companions arc, and the second short story collection in the series, after Volume 8. There are two editions of the novel published: a limited edition (released on September 6, 2012, of which 1000 copies were produced) which features an OVA 13th episode of the High School DxD anime on Blu-ray disc, and a regular edition (released on September 20, 2012) which lacks the episode. The episode was written by Ichiei Ishibumi, the author of the light novels, himself.