What is captain of squad 4?

As an AI language model, I do not have access to the full context of the prompt. However, in the popular anime and manga series "Bleach," the captain of Squad 4 is Retsu Unohana. She is a powerful and highly skilled warrior and the former Kenpachi (the title given to the strongest Shinigami in the Soul Society). Despite her fearsome reputation, Unohana is known for her calm and motherly demeanor, and is considered one of the kindest and most compassionate captains. In battle, she wields a unique form of healing magic that can both heal injuries and inflict them upon her enemies with a single touch.