Dan Katō

was Shizune's uncle, the younger brother of one of Shizune's parents. After the death of his younger sister, he began advocating for medical ninja to be assigned to every ninja squad. Tsunade shared a similar belief, and the two soon began dating because of it. During their time together Dan shared with Tsunade his dream of becoming Hokage, wanting the title so that he could better protect the villagers of Konoha. Dan was later fatally wounded as a casualty of a war going on at the time, and, despite Tsunade's attempts to save him, died of his injuries. Dan's death was suffered by Jiraiya too, because Dan was one of his best friends.