Hi Derty,
A one-year stay after a three-week trip sounds like a great plan, and meeting a few times in the Paris region before leaving is a smart way to find out if you travel well together.
One practical point to add while you plan. The Working Holiday Visa itself usually needs only a short list of papers, but a year in Japan can bring other paperwork later, such as a job offer, a change of visa category, or a partner or friend joining you from another country. In those cases, foreign authorities often ask for certificates like a birth certificate, a degree or a marriage certificate, and they may want them apostilled first. Japan and France both accept the Apostille system, so one stamp from the issuing country is normally enough. A late start is what usually causes delays.
If your travel buddy ends up being someone with documents from India, Apostille services in India are handled through the proper government channels and can take a few working days, so it’s better to begin early. Always check the latest document list on the official Japanese embassy website before you submit anything.
Good luck finding your companion!
Raj
More on the process:
HRD Attestation Services in India | Fast Document Apostille