Lupin the 3rd

Season 2, Episode 108

Episode Title: Zantetsuken's Lament

Air Date: 1979-11-05

Overview:

Even on vacation, Goemon has eyes for nothing except swordsmanship. A girl named Naomi takes on of the iron bars Goemon had wrapped in bundles of straw for the purpose of cutting practice. Her grandfather is a swordsmith, and he wants very much to make a katana better than Zantetsuken. Naomi puts energy into her support of her grandfather, and they discover Zantetsuken's secret: the high temperature of its blade. Who holds the true legendary blade?