As far as I can tell, there is no real horse that matches any of the above criteria.

• Forever Young did win back-to-back Saudi Cups, but they only finished 3rd in the Dubai World Cup, and that was inbetween the Saudi Cups and not afterwards.
• No Japanese horse has ever won the Prix de l'Arc de Triomphe.
• There is no overseas horse that competed in the Japan Cup twice in a row where they won the first year then were defeated by a Japanese horse their second year.
• Oguri Cap did win the Arima Kinen, and did have the most votes in history (it has since been exceeded), but they did not accomplish both in the same year. Neither Special Week, nor Tokai Teio, nor Kitasan Black ever received more votes than Oguri Cap did, and of those three, only Kitasan Black ever won the Arima Kinen.

Teio won the ‘93 Arima Kinen, no?

Special Week’s the only one of those three who hasn’t.

DeadlyZ said in comment #2581443:

Teio won the ‘93 Arima Kinen, no?

Special Week’s the only one of those three who hasn’t.

Yeah. The disqualifying point was "the most votes in history". Although Special Week, Tokai Teio, and Kitasan Black all won the popularity poll, Kitasan Black was the only one of those who won the popularity poll and the Arima Kinen in the same year. But even so, she did not beat Oguri Cap's 1990 vote record of 197,682 votes, which was not overcome until Chrono Genesis's victory in 2020. Interestingly enough, Chrono Genesis does qualify on just that singular point (most votes in history and Arima Kinen victory), however she has never been an Umamusume protagonist. The racehorse Efforia also qualifies on that point for her 2021 victory, but they've yet to even be made an Umamusume character.

Reference:

• https://en.wikipedia.org/wiki/Arima_Kinen