This takes place after the 13th chapter of OnS or after the 11th episode of Owari no Seraph season 1. Guren gets captured by the vampires and the Shinoa squad are sent to rescue him with the help of Narumi squad. Yuu's hopes are risen when he hears a description of a certain blue eyed vampire but when he sees this vampire again what colour will his eyes be? This is posted on archive of our own so if you want to see updates then i would recommend reading it over there.