Genzou Tamura is a 19-year-old construction worker, the third generation of his family in the trade, living in the working-class neighborhood of Beranme. When the urban developers of the Kuromoku Group move against the neighborhood, backed by Chainsaw Mika and Dynamite Dan, it falls to Genzou to protect his town using his reliable hammer. The ONA is a slapstick comedy adapted from Irem's Daiku no Gen-san video games, known in English as Hammerin' Harry.