Yes, Len does have a ponytail.
Len is characterized by his distinctive hairstyle, which includes short yellow hair that is specifically tied up in a ponytail. This particular style is noted for its unique appearance, resembling a "banana bunch." His hair color and style are key elements of his overall character design, complementing other features such as his blue eyes and an outfit that shares similarities with Kagamine Rin's, yet incorporates unique elements like his tie and longer, loose shorts.
