Jōsai Yūzūmuge (融通無碍城塞 Yuuzuumuge Jousai "Lit"; Free, Unfettered and Flexible Fortress) is a Shinigami that wasn't very well known in the history of the Gotei 13 and the Soul Society. He was never labeled as anything, and though a large contributor to the current Gotei 13, he was kept in the shadows by Genryūsai Shigekuni Yamamoto for unexplained reasons. Having revealed himself after the events of the Thousand-Year Blood War, he takes a more active role in the defense of the Gotei 13. Jōsai, among the Soul King Palace has been entitled the "Eternal Guard" (不変警備 Fuhen Keibi), due to his finding and construction of all Sekkisekki based constructs, and being the Gatekeeper for these fortresses.