Len is the main heroine in the main story of Kagetsu Tohya. She is capable of shifting between the forms of a black cat and an early teen human girl

She doesn't speak often, only once briefly in a scene of Kagetsu Tohya and during her interaction with White Len in Melty Blood Re-ACT. She seems to have a liking for cakes, and she dislikes taking baths.

Because she never talks, it's hard to really understand her personality, but basically she's the type of person that likes to quietly spend her time alone. Just like a cat, she is haughty and fickle, but prone to sudden bursts of attention-seeking craziness as well.