Kusatsu-Shirane Volcano, located on the border between Gunma and Nagano prefectures, is one of the most active volcanoes in Japan. Its eruptive history can be classified into Stages 1–3. During Stage 1 (0.6–0.5 Ma), Matsuozawa, a small stratocone, formed in the southwest area of the present-day Kusatsu-Shirane Volcano. The Oshi Pyroclastic Flow Deposit, which is the most voluminous eruptive product of Kusatsu-Shirane Volcano (8 km3 DRE), and the subsequent Komenashi, Maeguchi, and Aoba Lavas are the representative eruptives of Stage 2 (ca. 0.5–0.3 Ma). After a pause of 200,000–300,000 years, Stage 3 activity began at the present-day summit area, forming the Shirane (SPCG), Ainomine (APCG), and Motoshirane (MPCG) Pyroclastic Cone Groups in an area of approximately 3 km from north to south. At the SPCG and MPCG, block lava flows formed in the early stages of activity, followed by the formation of pyroclastic cones near the eruption centers of the lava flows. The most recent magmatic eruptions at the SPCG, APCG, and MPCG occurred at approximately 2000 cal yr BP, 1400 cal yr BP, and 1500 cal yr BP or later, respectively. Since then, small phreatic eruptions occurred in each pyroclastic cone group and formed several small craters and crater chains.