Yukippe, originally named Lucy Loo and later known as Lucy Adams, is Nate Adams' grandmother. As a child, she wore her hair in two braids featuring a small cowlick and had dark brown eyes. Her attire included a long red ankle-length dress worn over a plain white buttoned shirt, along with short white socks and black mary jane shoes. A defining feature is her spectacles, which hold a special crystal in the frame. This crystal, a childhood memento from her friend and future husband Nathaniel Adams, grants her the ability to see Yo-kai when peered through. It is the same crystal type Nathaniel used to create the prototype Yo-kai Watch.

She shows kindness and a caring nature, often prioritizing her family's welfare, a trait similar to Katie Forester, Nate's classmate and future wife. Yukippe shares a deep bond with Nathaniel, whom she befriended in childhood and later married. She maintains a loving relationship with her grandson Nate, seeking his help when encountering Yo-kai-related mysteries.

In *Yo-kai Watch: The Movie*, set in the past, Yukippe appears as Nathaniel's close friend. By the film's end, Nathaniel confides in her about the Yo-kai world and his Yo-kai Watch, securing her involvement in these events. In Nate's time, as an elderly woman living in Harrisville, she hosts his family after he receives a tip from Hovernyan, Nathaniel's Yo-kai companion. Before Nate departs, she reveals her ability to see Yo-kai through her crystal glasses, explicitly acknowledging the presence of his Yo-kai companions Whisper and Jibanyan, and requests they protect her grandson.

She makes a minor appearance as an elderly character in the "Little Grandma's Help" request within *Yo-kai Watch 2*. Her English childhood name, Lucy Loo, draws inspiration from real-life actress Lucy Liu, known for kung-fu film roles.