There is a horizontal stone chamber depositing a kurinuki-sekkan (literally, a coffin hollowed out a stone) on the outside of the northwest corner of the outer bank and when it was discovered, it was presumed to be a Baicho (smaller mounds by a Kofun).
外提の北西隅の外には刳坂（くりぬき）石棺を納めた横穴式石室があり、発見当初は陪塚（ばいちょう）であろうと推測されていた。