TOKYO — As Sotheby’s contemporary art auction heated up in New York last week, the Japanese billionaire Yusaku Maezawa sat on the floor of his living room here, streaming the auction live on his laptop and relaying bids for Jean-Michel Basquiat’s 1982 skull painting on his iPhone to a Sotheby’s specialist. After the price sailed past the $60 million guaranteed minimum, Mr. Maezawa — who hadn’t gone into the sale with his own limit in mind — felt that the competitive bidding reinforced the work’s enormous value.

“I decided to go for it,” Mr. Maezawa said in an interview at his home on Friday.

As Mr. Maezawa was bidding, Basquiat’s sister Jeanine Basquiat was about 7,000 miles away in New Jersey, hoping the auction would turn out well. When she heard that Mr. Maezawa had paid $110.5 million — the record price for an American artist at auction — she called her older sister, Lisane Basquiat, in California. “There wasn’t a lot to say,” Lisane said in a rare telephone interview. “We were speechless.”

If members of the Basquiat family are keepers of the Basquiat flame, Mr. Maezawa has now ensured it will continue burning, at least in the near future — in no small part because he posted about his purchase on Instagram and Twitter right after the auction.

“Vast numbers of people are aware of Jean-Michel Basquiat all over the world,” said the dealer Jeffrey Deitch, a longtime Basquiat expert, “and that is really only because of the immense price.”