Choujiro Sasakibe

He is the lieutenant (Vice-Captain) of the 1st Division. He is the least seen of all the lieutenants. During scenes of Head Captain Yamamoto in his office, Sasakibe acts more like a secretary and door guard than a lieutenant. In omake scenes, he is shown to have a penchant for tea. According to records, Sasakibe was able to master his Bankai before Juushirou Ukitake and Shunsui Kyouraku did. He did not participate in battles and did not use his Bankai in front of others in the entire existence of the Gotei 13 and was sometimes insulted because of perceived weakness. He declined to act as a substitute captain when a position as captain became vacant due to his loyalty to Captain-Commander Yamamoto.

At the beginning of The Thousand-Year Blood War arc Sasakibe is attacked by Vandenreich members. During this battle he used a bankai for the very first time in his life. However, his bankai gets stolen and Sasakibe is killed. Before his death he reveals this secret to Yamamoto. Sasakibe is later cremated atop a large funeral pyre as Yamamoto and other officers pay their last respects. (Source: Bleach Wikia)