Japan doesn't have UBI, but it's welfare system is extremely expansive as Article 25 of the Constitution guarantees a minimum standard of living through livelihood, housing, education, and medical assistance.
Additonally, Japan has spent decades thinking about this eventuality (at least since the 1970s), which is why Japan worked on the "Flying Geese" paradigm where Japanese public-private ventures would end up become major capital stake holders across Asia, the US, and Europe.
Taiwan (1960s onwards), South Korea (1970s onwards), and China (1980s onwards), and investments by what are now Master Trust Bank, Trust & Custody Services Bank, JTSB, and SoftBank.
The problem with UBI is not that people would stop working, it's that the value of whatever amount is given as UBI will drop very quickly due to inflation.
UBI is basically the same as saying "everyone should earn above average".
This is why the Australian 1907 Harvester Decision didn't merely settle on an amount (42 shillings a week) but also included a needs based indexing (support a wife and three children, to feed, house, and clothe them).
Additonally, Japan has spent decades thinking about this eventuality (at least since the 1970s), which is why Japan worked on the "Flying Geese" paradigm where Japanese public-private ventures would end up become major capital stake holders across Asia, the US, and Europe.