Infrequent megathrust earthquakes, with their complex cycles and rupture modes, require a high-resolution spatiotemporal record of tsunami inundation over thousands of years for more accurate long-term predictions. Geological records suggest that prior to the 17^th century, Mw>8 earthquakes on the Kuril Trench occurred at intervals of several hundred years. However, uncertainties remain about the rupture zone, owing to limited survey areas and chronological data. Therefore, we investigated tsunami deposits in a coastal wetland of southeastern Hokkaido, Japan, to characterize tsunamis originating from the Kuril Trench over the last 4000 years. On the eastern Erimo coast, ten sand layers were identified that exhibit the common features of tsunami deposits, such as a sheet distribution of several hundred meters, normal grading structure, and a sharp basal contact. According to numerical simulations, the 17^th-century sand layer could be reproduced by tsunamis generated using a multiple rupture zone model (Mw~8.8). We used high-resolution radiocarbon dating and tephras to correlate tsunami deposits from the last 4000 years with those reported from regions ~100 km away. The tsunami history revealed by this study show good agreement with those of the compared regions. However, paleo-tsunamis reported from regions > 200 km away include some events that differ from those in this study, suggesting a diversity of Mw>8 earthquakes in the Kuril Trench. We clarified the history and extent of earthquake-generated tsunamis along the southwestern end of the Kuril Trench, which was previously unknown. Our results provide a framework for magnitude estimations and long-term prediction of earthquakes.