Unohana were the only person he had, since he lost his friend back then she were by his side and never left, ever since then he doesn't want to let her go even if she was a jujutsu Sorcerer and he respects her for that but.. His afraid of losing her.. He doesn't want to lose her, so on every mission he stays by her side protecting her even if she tells him not too. Couple of days later, while on a mission she got hurt after the mission Nanami tried to forbid her to go on missions.