HAWTHORNE, Calif. — When Yusaku Maezawa took the stage here at one corner of the SpaceX factory floor, the founder of the online Japanese clothing company Zozo explained that he did not just want to be the first private citizen to circle the moon.
“I choose to go to the moon, with artists,” Mr. Maezawa said, echoing President John F. Kennedy’s speech in 1962. He announced his intentions to travel to space with an unconventional crew during a news conference Monday evening where he shared the stage with Elon Musk, SpaceX’s founder.
Mr. Musk is usually the center of attention at events like these. But he had reasons to share the spotlight with the Japanese billionaire: Mr. Maezawa had already put down a deposit for a flight aboard SpaceX’s next-generation rocket, the B.F.R.
“A very significant deposit,” Mr. Musk said.
While SpaceX’s Falcon 9 and Falcon Heavy rockets have been significant technological achievements, its engineers have started to turn their attention toward the B.F.R., a much more ambitious vehicle that Mr. Musk hopes will one day make regular trips to and from Mars, part of his vision of spreading humanity across the solar system.
Mr. Musk said B.F.R. was still a small project at SpaceX — less than 5 percent of the work, he estimated — but was one that would grow in the coming years. Mr. Maezawa’s four- to five-day trip moon trip would not occur until 2023 at the earliest.
Although he would not discuss how much Mr. Maezawa is to pay for his trip, Mr. Musk made clear it would make a significant contribution to the development costs. Mr. Musk, who has experienced considerable tumult in recent months, even said that Mr. Maezawa’s willingness to give SpaceX so much money for a risky venture has “done a lot to restore my faith in humanity.”
Mr. Musk estimated development costs at roughly $5 billion. “I don’t think it’s more than 10, and I don’t think it’s less than two,” he said.
In an interview after the news conference, Mr. Maezawa said he had started thinking about a moon trip about five years ago. At first, he contemplated a Russian offering, marketed by the space tourism firm Space Adventures.
Later, he contacted SpaceX, which was getting closer to launching its Falcon Heavy rocket, capable of sending missions to the moon. Last year, SpaceX announced that it was in discussions with two people for an around-the-moon trip that would take place in late 2018. On Monday, Mr. Musk said that Mr. Maezawa was one of those people.
However, SpaceX decided not to undertake the expense and effort needed to ensure that the Falcon Heavy was safe enough to carry humans, and the tourist trip was deferred.
Discussions then moved to using the B.F.R. for the moon trip, even if that meant waiting five years. Mr. Maezawa said he was willing to wait longer, as long as he was still the first private person to get to the moon.
Mr. Maezawa, 42, who may be best known in the United States for his purchase in 2017 of a 1982 painting by Jean-Michel Basquiat for $110 million, said he did not like to be alone and so he would invite five to eight artists and performers to accompany him, part of a project he called Dear Moon.
Mr. Maezawa also said that art contributed to his ultimate hope of world peace. “Art makes people smile, brings people together.”
He added that he looked forward to seeing the works of art that would be inspired by the trip and wondered what masterpieces Basquiat, who died in 1988, might have created.
When asked whether a trip around the moon was the most beneficial way to spend his fortune, Mr. Maezawa acknowledged the philanthropic efforts of other entrepreneurs, but said, through a translator, “I want to contribute to society in a different way.”
“So maybe 10 years from now, people will be laughing I paid so much, but somebody needs to make the first payment,” he added. “Otherwise, space development is not going to evolve. That’s why I think I should be the one to do this.”
Until now, only 24 people have made the quarter-million-mile journey to the moon — all NASA astronauts during the Apollo program in the 1960s and 1970s. The trajectory of Mr. Maezawa and his guests would be similar to the one taken by the Apollo 8 astronauts in 1968 as they swung by the moon but did not land.
Liftoff aboard the B.F.R. is still be years away, on a gargantuan rocket that would offer much more spacious accommodations than the Apollo astronauts had. At the news conference, Mr. Musk described the latest iteration of the design, which eventually is to carry 100 people to Mars.
(The “B” stands for “big;” the “R” is for “rocket.” In public, Gwynne Shotwell, SpaceX’s president, states its full name as “Big Falcon Rocket.” Mr. Musk and the company’s news releases have remained ambiguous about what the “F” stands for.)
Mr. Musk said that the rocket would be test launched many times in the years to come, including possibly an uncrewed flight around the moon before Mr. Maezawa and the artists went aboard. “That would be wise,” Mr. Musk said.
On the stage Monday night, Mr. Musk, showered praiseful adjectives like “bravest” on Mr. Maezawa.
“This is a dangerous mission,” Mr. Musk said. “Definitely dangerous.”
Mr. Maezawa seemed unfazed by the potential dangers, saying during the interview that he trusted the SpaceX team. “Everyone around me, they are very supportive of my adventures,” he said.
He also noted that his birthday and the assassination of President Kennedy share a day — Nov. 22 — 12 years apart. “I feel destiny,” he said.
Mr. Musk, when he was asked on the stage when he would go to space, was uncertain. “He did suggest that maybe I would join on this trip,” he said. “I don’t know.”
“Yeah, yeah, yeah,” Mr. Maezawa said. “Please.”
“Maybe we’ll both be on it,” Mr. Musk said.