- #42
Shunsui lot his brother and his brothers wife. And he made promises to both and those promises converge in protecting Nanao.
Thus its obvious shunsui made sure Nanao would never have to fight or be in some dangerous situation.
It also was foreshadowed in Shunsui/Ukitake VS Yamamoto fight where she had a huge freak out and Shunsui expressed regret of having brought her there.
Shunsui carried out his promise too well. She has never been injured. She never fought. She never experienced fear in battle.
By allowing Nanao to fight here and take the front (Which is yet again theatrical allusion with background and foreground of the stage)), Shunsui is actually trying to make peace with his regrets and allowing Nanao to graduate into being an adult.