“Mr so-and-so” in Japanese
Short answer
Mr so-and-so in Japanese is “誰それ” (daresore). Full meaning: a certain someone, Mr So-and-so.
Other ways to say “Mr so-and-so” in Japanese
某氏
boushi a certain person, unnamed person, Mr. So-and-so, a certain someone who shall remain unnamed
何がし
nanigashi certain amount, some; certain person, Mr So-and-so, a certain ...
何とやら
nantoyara for some reason or other, somehow; whatsitsname, what-you-call-it, Mr. so-and-so; and so on, and you know the rest
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