Mr. Yamada is the husband of Mrs. Yamada and is the father of Seina and Yoshiko. He, along with his wife, operated a small, ill-repaired grocery store in Okayama Prefecture, that doubled as the Yamada home. Mr. Yamada, as well as Mrs. Yamada, often lamented about the huge doctor bills that the family suffered from as a result of the constant injuries Seina suffer as a result of his bad luck.
Of course, when Seina went off to the Galaxy Police Academy and was placed as the commander of the Kamidake II, the GP placed his pay into an escrow account to be handed to him upon his graduation - pay that was equivalent to a fleet commander's compensation! The GP then sent the interest from that account back to the Yamadas - which was a quite sizable chunk of money! Mr. Yamada used that money to not only build a spacious new home for the family, but also to build a large supermarket in place of the small grocery he operated.