Tenri Ayukawa

A shy and reticent childhood friend of Keima, who was a former next-door neighbor and classmate until the Katsuragi household relocated seven years ago. Ten years later, when she and her mother visits Keima's house over the summer vacation, Tenri is exactly the same as before: the reserved nature and hairstyle, and the bubble wrap in her hands. ~!At first, it is believed Tenri possesses a runaway spirit within her, who manifests as a much more confident, strong, stoic version of herself with eyes visible. She is able to switch with the other personality at any time, or communicate with her in her head, and vice-versa. The other personality, if not in possession of the shared body at the time, can communicate to other people including Tenri through her reflection via a reflective surface. The personality reveals to Keima that her existence is not a 'Weiss' (former name for runaway spirits, but those that were responsible for ending the Old Hell, and sealing away all the runaway spirits. The entity, named Diana, merged with Tenri during a school trip, when Tenri and Keima were trapped in an underground cave and surrounded by many runaway spirits, enabling the two to escape.!~ (Source: Wikipedia)