200 years ago, Zenmai Zamurai (Zennosuke at that time) was a thief by profession (albeit not a very skilled one). While stealing from a house one night, he fell down a well and died. He was then resurrected by Daifukunokami (The god of Bounty:大福の神) and a wind-up key (zenmai:ぜんまい) was placed on his head. If the key winds down, Zennosuke dies