Kawachi Otsuka Tomb (reference site for the Otsuka Tomb) is a keyhole-shaped tumulus. The mound is approximately 335 meters long, with a circular rear section of approximately 185 meters and a front section of approximately 230 meters wide, and a moat 35 to 70 meters wide. It is the fifth largest tumulus in Japan and is said to represent the final stage of the keyhole-shaped tumulus, which changed shape over time. It is believed to date from the second half of the 5th century to the end of the 5th century. The tumulus straddles Nishi-Otsuka in Matsubara City and Eganosho in Habikino City, dividing the area into east and west.