[RRW]

Spoiler for kyon name:

first "Yamada Tarō" is Japanese equivalent of "John Smith"
Yamada and Tanaka have similar meaning ("mountain ricefield" and "middle of the ricefield")
Tanaka is much more common name than Yamada in japanese
Taro means "eldest son" (assuming that he has no older brother/sister)
along with baltakatei Japanese surnames chart. it's possible that kyon name is "Tanaka Taro". the name is fit to him as "normal/usual person"

this is what I think. it can be wrong or right.