Agreed, those are good second passports to have.
> I think Japan does not allow for dual citizenship though.
Like Japan, China and the US also do not allow a second citizenship through naturalization. The US oath of allegiance requires you to "renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty". The loophole is that most countries don't allow you to renounce your citizenship just by informing some foreign flunky, so just saying it doesn't make it so. For naturalization, none of China, Japan or the US require documentary evidence that you are no longer a citizen of another state.
