20 y/o planning to move to Japan as a personal trainer. What entry paths actually work?

Hey everyone,

I am 20, from Saudi Arabia, and Japan is where I want to build my life. I am giving myself 5 to 7 years to prepare. By then I will have a Kinesiology degree, CSCS, Nutrition and Corrective Exercise certs, N2 Japanese, and an online coaching business already running.

I know fitness jobs alone will not get me a visa. From what I have researched the realistic entry options seem to be English teaching via JET or Eikaiwa, the Engineer or Specialist in Humanities visa through a Japanese employer, a language school student visa, or a Business Manager visa if you have the capital.

I am drawn to cities like Fukuoka, Sendai, Nagano, or Kyoto. Somewhere with nature close by and a real community feel.

A few honest questions:

1.Which entry path actually works best in practice for people who are not going the English teaching route?

2.How realistic is transitioning into fitness once you are already there?

3.What are the biggest mistakes people make in the first year?

4.Anything you wish someone had told you before you moved?

Appreciate any honest answers. Thank you.