TWOV Sanity Check & Question - US → Layover JP → Shanghai → Chengdu(?) → HK → Beijing/Shanghai → US

We're in the process of trying to get our L Visa but there's a likelihood it may not be approved in time (our flight's next week) so was curious if we could make this trip with a TWOV instead:

1. US → Layover in JP 10 hr →Shanghai

2. Shanghai → Chengdu via flight - would this be allowed?

3. Chengdu → HK

4. HK → Beijing

5. Beijing → Shanghai (Train)

6. Shanghai → US

Both are US citizens. Appreciate any insight/feedback. Thanks!