Looks like that's what may be happening:
Source: The Japan News by the Yomiuri Shinbun
Govt eyes converting Izumo to aircraft carrier
The Yomiuri Shimbun
8:23 pm, December 26, 2017
The government is considering remodeling the Maritime Self-Defense Force’s largest-class destroyer, the Izumo, into an aircraft carrier on which fighter jets can take off and land, The Yomiuri Shimbun has learned. If the plan materializes, it will be the first aircraft carrier to be possessed by the Self-Defense Forces.
According to multiple government sources, the government aims to begin operation of the aircraft carrier in the early 2020s, and it intends to maintain its interpretation that Japan cannot possess an aircraft carrier with attack capabilities, by using the envisaged aircraft carrier for defense purposes, such as using it as a refueling base in defending remote islands.
The government assumes that the new aircraft carrier will carry U.S. forces’ F-35B fighter jets (see below), the sources said. By strengthening Japan-U.S. cooperation, the government aims to prepare for threats posed by North Korea and China.
The Izumo is a destroyer with a large deck, and its shape is similar to that of an aircraft carrier. It has an overall length of 248 meters and a full load displacement of about 26,000 tons. It is said that the vessel is capable of carrying 14 helicopters. If it is remodeled into an aircraft carrier, it likely will be able to carry about 10 F-35B fighter jets, according to the sources.
In the remodeling, the deck’s heat resistance will be enhanced so that it can withstand the heat produced by the jet engine of an F-35B fighter jet, the sources said. A specific remodeling method will be examined going forward, including a plan to build a slope into the deck to assist aircraft in taking off, much like a ski jump.
The Defense Ministry aims to appropriate research expenses in the fiscal 2019 budget, the sources said.
The government also is considering deploying F-35B fighter jets to the Air Self-Defense Force. However, if F-35B fighter jets are loaded onto the envisaged aircraft carrier, it would directly mean Japan’s acquisition of the ability to hit enemy bases. Therefore, the government will decide the issue based on discussions for the revision of the National Defense Program Guidelines at the end of 2018.
The purpose of possessing an aircraft carrier is to promote integrated operations between Japan and the United States through refueling U.S. forces’ aircraft on the aircraft carrier.
Under the security-related legislation that went into effect in March 2016 and the new Acquisition and Cross-Servicing Agreement (ACSA) that took effect in April 2017, Japan is now able to refuel U.S. forces’ aircraft in a wider range of situations, such as exercises in peacetime and preparation for action in case of emergencies.
The use of a Japanese aircraft carrier by U.S. forces will help enhance the ability to defend remote islands and the MSDF’s defense capabilities. In case of enemy attacks on remote islands or MSDF fleets, if U.S. fighter jets can land and refuel on the aircraft carrier deployed at a place an appropriate distance from the enemy, the ability to deal with the enemy will be increased.
If U.S. military bases in Japan are destroyed in case of a contingency, the aircraft carrier will serve as a substitute runway.
In fact, North Korea has mentioned the possibility of attacking U.S. military bases in Japan with ballistic missiles. In case of an emergency on the Korean Peninsula, runways at the bases could become unusable. At the same time, China is expanding its maritime advances. Given these situations, building up the ability to defend remote islands is an urgent issue facing Japan.
The government has cited an aircraft carrier with attack capabilities as an example of armed forces with war potential, the possession of which is prohibited under Paragraph 2 of Article 9 of the Constitution.
However, a senior Defense Ministry official said, “If it is used for defense purposes, it will not fall under the category of an aircraft carrier with attack capabilities.”
■ F-35B fighter jet
A state-of-the-art stealth fighter jet jointly developed by nine countries, including the United States and Britain. It is capable of performing short takeoffs and vertical landings. The aircraft is expected to be used for missions on the front line where it is impossible to ensure long takeoff distances and for other missions. It is operated by the U.S. Marine Corps, and has been deployed at the marines’ Iwakuni base in Iwakuni, Yamaguchi Prefecture, from January 2017.