Residence card

Hello everybody
Hope all of you are safe !!

I have few questions please if anyone can help .

- I have residence card in japan for 3 years start from October 2019 and end in October 2022. ( work visa )

- I departed Japan in 25 December 2019 , for business trip and I resign in May 2020

Now the questions I have as follow :

- is my residence card still valid .

- If is still valid should I back to japan before 25 Dec 2020 ??

Now I am establishing Japanese company with Japanese partner , we should have it established on 1st Dec . ( my position is Co-founder ) with 40% share .

Should I update my new work to immigration ?

Sorry for much questions but I just want to know how should I act .

Thanks to everyone in advance .

Changes that relate to resident status (such as changing employer, school, marital status, etc.) need to be reported to the immigration authorities within 14 days of that change happening. So of course you need to report your work change.

By the way, gestablishing a companyh requires a different type of visa/resident status from one of the gwork visah types, meaning employer-sponsored ones (unless your partner is hiring you as an employee). So this is not going to be just a change of employer/work type.

I resign in May 2020
So you need to notify immigration within two weeks (some time in June latest - months ago). If you have not done that, then that is a problem. You could get another job in the same category, that needs to be done within a few months (I think 3 months - but that is not my area of expertise).
If you are now establishing a different/new company, if you are an employee in the same work category, then your current visa might apply. If you are going down the business manager/investor route, you have several problems, including not having the correct residence status, and not having the correct position in the company.
Get yourself to an immigration lawyer.