is a Murakumo Unit
who was sealed in the Sheol Gate
. She was programmed to terminate anyone she deems as hostile subjects that came near the Gate. Nu-13 is also shown to have a split personality, split between an emotionless girl when around others, and a yandere
when around Ragna the Bloodedge
, though this may be how she was programmed to act. Nu-13 wants to absorb Ragna and have him join her in destroying the world, because she, too, possesses a piece of the Azure Grimoire
(although neither she nor Ragna realized the pieces they possess were actually imitations). When Ragna refuses to join her, she decides to take him by force.
She, as with Noel
, was made as a replica of Saya
, Ragna and Jin's
sister. They seem to share some of Saya's memories, though nothing congruous. In the true ending, she tries to merge with Ragna by falling with him into the Cauldron. However, Noel thwarted her efforts and saved Ragna's life. Nu dies after falling back into the Cauldron and failing to fuse with Ragna.