Japan did not do anything. literally nothing, no lockdowns or mandates of any sort.

They have lowest mortality from COVID. What if the right policy all along was to do nothing?

The Japanese did plenty. They cancelled festivals and sporting events, switched many schools to distance learning, widely wore good masks, got tested, traced contacts, closed entertainment venues, etc.

The government did not order this. The citizens did it voluntarily when asked to by their government.

They definitely have a mask mandate.

But my question still remains, what exactly does the author suggest?

https://jp.usembassy.gov/covid-19-information/ There is also travel restrictions. Nothing is not the right word to use for Japan's covid policy.

Technically there are never mask mandates by gov, but just 99.8% (I assume) of people wear mask.

Correct, the Japanese people naturally wear masks if they feel sick. This fact, combined with Tokyo being one of the most densely populated cities, should be plenty evidence for how effective masks are.

Well, there must be an indoctrination process happened sometimes in the history. After all, facial masks are not invented in ancient time people are not used to wear them.

So when the obedient Puritan people coming to this land. They are very cooperative in helping maintaining the community.

Through some indoctrination, they learned to stand up with their own wills. Turns out coins indeed always have 2 sides, right? When the individuals learn to stand up coercion with their own wills, they would stand-up against facial masks, vaccines, quanrintaines, etc.