24-hour Visa-free Transit, MUST I have the 3rd Country Visa?

Hi, I'll be travelling from the USA to Japan, with a short 1 hour stop in Dalian, China, then to Beijing with an 18 hour layover. So total time in China is less than 24 hours. My question is, for the 24-hour Visa-free Transit, must I have a Visa to Japan to show, or will just having my onward ticket to Japan be sufficient? Japan does not require a Visa for my short one week visit. But will China require me to have a Visa to Japan to be able to leave the airport in BJ?

Thanks!