Len is a quiet and mysterious girl who appears in the Melty Blood series, which is a fighting game spin-off of Tsukihime. She is a familiar, a cat-eared succubus created by Aoko Aozaki and later serves Arcueid Brunestud and Shiki Tohno. Len is known for her calm demeanor, dream-manipulation abilities, and her significant role in the story, often acting as a silent observer or guide for the main characters. She is a fan favorite for her unique abilities and memorable design.