TOKYO — Yusaku Maezawa, the billionaire entrepreneur who last month became the first Japanese civilian to travel to the International Space Station (ISS), said Friday he now plans a trip to the Mariana Trench, the deepest location on Earth.

Maezawa revealed the exploration project at a press conference at the Foreign Correspondents' Club of Japan in Tokyo, saying that "it's been almost decided what kind of submarine will be used and how long the trip will be."

Details of the plan will be announced later, he added. The billionaire said in a live radio broadcast from space last month that he next wanted to fulfill his dream of going to the deepest place on Earth.

"Since I've come this far already, I'm thinking of diving into the deep sea. I want to go high and low," he said at that time.

Maezawa, widely known for his eccentric behavior such as giving away money on Twitter, has distinguished himself from other Japanese entrepreneurs who are generally considered risk-averse.

A Russian Soyuz spacecraft carrying Maezawa was launched from Kazakhstan on Dec. 8 last year to the ISS and he returned to Earth on Dec. 20.

The founder of major online fashion retailer Zozo Inc. plans to orbit the Moon with US firm SpaceX's Big Falcon Rocket in 2023, in the first such trip organized by a private company. He said after his return from the space station that he also hopes to visit the Moon.

With his planned orbit of the Moon scheduled about a year from now, the billionaire said he is hoping to reveal who will accompany him on the trip shortly. He has previously said he wants to take six to eight world-renowned artists with him.

“Space now,” was what Japanese billionaire Maezawa wanted to tweet for years. He finally really did it, from the International Space Station, reported AP. “The space market holds so much potential,” he said.

Maezawa, who heads a company called Start Today, is preparing to invest in various businesses which may develop from the ongoing research by NASA, the Japanese equivalent called JAXA and others.

But he wants first to recover from his recent celestial adventure: returning to life with gravity has proved heavier than he’d expected, he said.

"I had underestimated zero gravity. I have become newly aware of the heaviness of Earth's gravity," he said at the press conference.

Maezawa, 46, blasted off in a Russian Soyuz spacecraft along with a Russian cosmonaut Dec. 8, becoming the first self-paying tourist to visit the station since 2009.

He returned to earth after spending 12 days at the orbiting outpost, where he took videos of himself clowning around in weightlessness, shaping water droplets into bubbles and punting a golf ball drifting toward a flag in the spacecraft.

He said he would like to tweet “moon now” next. “I don’t know when exactly I should tweet that,” he said, as he wouldn’t be landing on the moon. “Maybe when we get to the back side of the moon.”

Maezawa has more than 11 million Twitter followers and has emerged as a flamboyant celebrity known for a free-wheeling managerial style that’s rare in Japan’s conformist, staid business world.

How much Maezawa paid for his voyage has been the topic of much speculation and skepticism. Reports put the price tag at more than $80 million. Maezawa declined again to disclose the cost.

But he said living in space has him appreciating the everyday more: the wind, the changing seasons, smells and sushi. — Agencies