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Major element oxides and Cl of dispersed (invisible to the naked eye) volcanic glass shards were measured in clastic sediments of the central Japan Trench recovered at Site M0090 during International Ocean Discovery Program Expedition 386, Japan Trench Paleoseismology. The glass shards were extracted from two giant piston cores, Core 386-M0090B-1H (Sections 1H-15, 80 cm, to 1H-14, 50 cm) and Core 386-M0090D-1H (Sections 1H-14, 0 cm, to 1H-13, 50 cm), which together represent 180 cm of the sediment. High-resolution sampling with 1 and 5 cm spacing (65 samples) aimed to better define the stratigraphic position of the To-Cu marker ash (~6000 y before present), which had previously been identified within this interval. Electron microprobe analysis reveals low-K volcanic glasses (<1.5 wt% K2O; ~67% of the glass data) and medium- and high-K glasses (>1.5 to 5 wt% K2O; ~33% of the glass data) in all 65 samples. The low-K volcanic glasses display the typical compositional characteristics of volcanic glass from the Towada volcano in Northern Honshu and may be mostly of To-Cu origin. The medium- and high-K glasses are likely an assortment of volcanic glasses produced during various Holocene and Pleistocene explosive eruptions of the Honshu arc volcanoes. Variation in grain size fraction, magnetic susceptibility, bulk density, and natural gamma radiation of the sediment sequence sampled suggests that all glass shards were emplaced in turbidite flow either syn- or posteruptively with a major explosive eruption of the Towada volcano.