Excavated sporadically for over thirty years, Ōgata in Kashiwara City and Mori in Katano City are the largest-scale Kofun Period ironworking sites in Osaka Prefecture, Japan. Large numbers of forging slags have been unearthed from both sites, which alongside partially preserved hearth features, provide the bulk of evidence for ironworking. Following methods developed by French archaeometallurgists, novel analyses of these forge slags correlate different slag materials with different forging activities. This has allowed for more precise reconstructions of the kinds and range of ironworking activities at these two sites. This project combines these new analyses with new radiocarbon dates, charcoal analysis, and legacy data from prior slag analyses to illustrate the contrast in ironworking technologies at the two sites as well as differences in fuel preferences and ironworkers’ relationships to local forest landscapes.