SERAPH OF THE END: KYUUKETSUKI SHAHAL

The OVA story is set before the main story's "Battle in Nagoya" arc. The Shinoa Squad is ordered another mission from Guren to rescue a human girl named Riko from a mysterious vampire Shahal, and bring her back to her family. But Ferid and Crowley also appear when they find Shahal. Can Yuichiro save the girl? — Description from AniList community (anilist.co).