This is Tatsuro Yamashita's talent agency:
https://www.smile-co.jp/artistThey also represent his wife, Mariya Takeuchi.
Since Plastic Love went superviral on Youtube they are definitely aware of the Western surge of interest in City Pop. They rereleased the single to capitalize on it.
Tatsuro still tours and makes radio appearances. He was supposed to tour last summer but it was cancelled because of coof regulations. He rereleased his most popular single "Christmas Eve" just a few months ago.
Collabing with a western singer known for going viral on youtube, who deeply loves City Pop as a genre, and who is managed by a Japanese company, is not outside the realm of possibility at all imo. It was probably a pretty big stretch at the time she debuted, which is when she told Cover about it and probably when they tried.
I'm not saying anything we do as fans could make this come closer to happening. But it's not like it hurts to try. Getting Dante to make a personal video was a pretty good get last year. Maybe this is the next boss.