Kokumin nenkin / kosei nenkin: basic question!

[RetireJapan]

Well, I believe pension contributions have a maximum, regardless of income above that.

So Yoshiki from X Japan is probably okay

[kuma]

Could it be that the employment portion would be under kosei nenkin but the self-employment portion would be under kokumin nenkin... which has already been covered under kosei nenkin, so there would be no additional contributions required from employee or employer?

Yes, the above holds true. I've answered my old hypothetical Q as I'm now in this actual situation and have clearer info. Posted in case useful to others.