Aileen is a female alien and agent who has a long working and romantic relationship with K.
She lost her former partner to an alien shape-shifter called an Inanimate. She is later assigned another partner named Eidi, whom she treats similarly to K's treatment of J, such as not being allowed to drive. Like K, she is a legendary agent on her home planet.
She is a blue skinned humanoid, and members of her species can transform their hands into tendrils.