Kisuke
Urahara

Kisuke Urahara runs a small candy shop in Karakura Town, wears a striped bucket hat, and apologizes constantly. He is also the exiled former captain of the 12th Division, founder of the Shinigami Research and Development Institute, and the inventor of the Hogyoku, the object nearly every war in the series is fought over. A century before the story, Aizen's Hollowfication experiments framed him; Urahara fled to the Human World with Tessai and the eight Visored he could not cure, and he has been quietly preparing for Aizen ever since.

His shop is where the story's machinery lives. He restores Ichigo's Shinigami powers with a brutal shattered-shaft training, teaches him Bankai in three days using a device meant to take decades off the process, opens every door to Soul Society and Hueco Mundo the cast ever walks through, and hid the Hogyoku inside Rukia's soul, a decision he apologizes for on his knees. In the Fullbring arc he and Isshin restore Ichigo's lost powers with a sword charged by the Reiatsu of Soul Society itself.

In the Thousand-Year Blood War he is everywhere the plot needs a scientist: he develops the shin'eiyaku pills that let captains steal their Bankai back from the Sternritter, coordinates the invasion of Wahrwelt, and stands at the front of the assault group with Byakuya and Shinji when Gerard Valkyrie drops out of the sky. The show has still never fully opened him up. Yoruichi trusts him completely, Aizen respects him, and everyone else has learned to be nervous when the hat tilts down.