One half of a two-man scheme to heist Wanyuudou's diamonds. Depending on which version you're looking at, Yamada's circumstances shift pretty wildly. In the manga, he's just a regular guy who stumbles onto the diamonds alongside his buddy. But the 1968 anime gives him more of a setup—he works as an appraiser at a jewelry store, with his friend handling clerk duties. When Junko brings in her diamond, Yamada lowballs it, telling her it's worthless so the two can pocket it themselves. From there, they get greedy and plot to steal Wanyuudou's stash after he deliberately tips them off about where it's hidden, setting them up for a trap.
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