The Tokachidake volcano group, central Hokkaido, is one of the most active volcanoes in Japan; three magmatic eruptions occurred from the crater area on the northwestern flank of Tokachidake in the 20th century. The Sandan-yama, Kamihorokamettokuyama, and Sampōzan edifices are on the southern flank of the volcano, and the first two bound the west-facing Nukkakushi crater. Although fumarolic activity and hydrothermal alteration are ongoing at Nukkakushi crater, its eruptive history remains unknown. Therefore, we performed a geological investigation of the Nukkakushi crater area. Based on topographical features, we inferred the following eruptive history. Sampōzan and Kamihorokamettokuyama formed during ca. 70-60 ka, after which the northern flank of Sampōzan collapsed and a new edifice (Nukkakushi volcano) was built within the collapse scarp. Finally, the collapse of the western flank of Nukkakushi formed Nukkakushi crater—perhaps during the Holocene, according to previous work. We identified eight Holocene eruptive products generated from the Nukkakushi crater area, the most recent of which was generated from a crater on the western flank of Sandan-yama sometime since the early 18th century. We also recognized three debris avalanche/landslide deposits that were generated within the last 750 years. Comparing the eruptive products of the northwestern crater area of Tokachidake with those of the Nukkakushi crater area revealed that magmatic eruptions from the two craters alternated until 1.8 ka. Their distinct magmatic compositions suggest the simultaneous existence of two isolated magma systems beneath Tokachidake and Nukkakushi, at least until that time. Since 1.8 ka, magmatic eruptions at the northwestern crater area of Tokachidake and phreatic eruptions at the Nukkakushi crater area have occurred in parallel. Moreover, around Nukkakushi crater, small-scale collapses/landslides have occurred. Previous studies recognized hydrothermal changes at Nukkakushi crater area, originating from the northwestern crater area of Tokachidake around the last two magmatic eruptions; it is therefore presumed that the Nukkakushi crater area was hydrothermally altered, even during periods of little eruptive activity. Such continuous and pervasive hydrothermal alteration explains the frequent collapses of edifices. The parallel yet contrasting eruptive activities in these adjacent areas are important for forecasting future eruptive activities and mitigating volcanic hazards.