Saya and her team infiltrate the Yanbaru laboratory. David had learned that the U.S. military is conducting experiments underground to build artificial Chiroptera. There he discovers a mysterious keyword called "Delta 69". Then, a Chiropteran swoops down on Saya's party underground, where they can take no refuge. In order to escape from their subterranean trap, they will have to defeat the creature. Who can save Saya and her party from this desperate predicament?