Phonon (フォノン) is an unallied In-Birth who has recently awakened to her powers. She is an aspiring writer who admires all kinds of supernatural things. She first made her debut in the arcade launch of UNDER NIGHT IN-BIRTH Exe:Late[st]. Adrift in a world of mystery, the "Chemeti" Having a strong sense of power, Phonon leaves the EFG, a student self-defense force known for their strict rules, so she can use her powers more freely. Her behaviour is not unlike a normal student's, going through a sensitive stage and wanting to find their "true self" amid the exhaustion of daily life. She believes her In-Birth powers are proof of awakening to her true self. As such, she uses her power against other under the darkness of night. Little does she know that there is someone else who also moves shadows who knows her "false self" from before she awoke.