Toyota doesn't require synthetic oil for subsequent changes I believe, but it definitely comes with it from the factory. In fact, quite a few Toyota comes with our 0W-20 from the factory. Take a look at the attached Toyota TSB. Although an old one, you can see Toyota switching the recommendation from generally 5W-30 to a synth blend 5W-20 and fully synth 0W-20. This was prior to the new Tundra. When the new Tundra came out, more engines were switched over.
Also, switching to and from Synth to conventional is a myth. For very old vehicles (15 years +), the seals and gaskets materials used were not compatible with fully synthetic oil because they are so thin and smooth. And a lot of the additives that goes inside a synthetic oil shrinks or expands the gasket too much causing leaks. However, the technology and material used in engine parts since has been improving. They are compatible with no problems at all with switching back and forth.
Finally, Nippon Oil does make passenger vehicle lubriants. Please see attached links. In fact, Nippon Oil works with pretty much all asian vehicle manufacturers on some products.
(Lubricants) ENEOS - Nippon Oil Corporation -
Eneos USA