29SS submarines

This submarine class has a non-nuclear air-independent propulsion (AIP) propulsion plant using improved lithium-ion batteries for enhanced silencing and operational flexibility. These submarines will also have improved sonar and weapons systems. The lead ship Taigei will serve as a test bed for the rest of the class, allowing more rapid technical upgrades to the other submarines within this class.^[54][55]

30FFM frigates

In August 2017, the Acquisition, Technology & Logistics Agency (ATLA) selected Mitsubishi Heavy Industries (MHI) and Mitsui Engineering and Shipbuilding (MES) as the prime contractor and subcontractor to construct the frigate. In addition, the agency also selected a completely new design of the vessel (30DX). The new ship class is set to replace the Asagiri-class destroyers and Abukuma-class destroyer escorts.^[56]

Amphibious transport vessels

At a press conference held on February 16, 2021, Defense Minister Nobuo Kishi announced that the Japan Self-Defense Force (JSDF) established a joint amphibious unit equipped with three new transport ships by 2024. These units will consist of one medium-sized Logistics Support Vessels (LSV) capable of carrying about 1,700 long tons (1,700 t) of cargo and three smaller Landing Craft Utility (LCUs) vessels with each capable of carrying 350 long tons (360 t) of cargo and operating in shallow waters. Although the Japan Maritime Self-Defense Force (JMSDF) has been basically responsible for the operation of the vessels, these vessels will be operated by a joint unit as the focus is on supporting the Japan Ground Self-Defense Force (JGSDF) and other forces operating in remote Southwest Islands, including Okinawa.^[57][58] The JSDF activated Japan's first marine unit since World War II on April 7, 2018, and the marines of the Amphibious Rapid Deployment Brigade (ARDB) are trained to counter invaders from occupying Japanese islands along the edge of the East China Sea.^[59]

Next-generation offshore patrol vessels (OPV)

On 30 June 2022, the Japan Ministry of Defense (MOD) announced the construction of 12 offshore patrol vessels (OPV) (pictured) for the Japanese Maritime Self-Defense Force (JMSDF) at a cost of ¥ 9 billion (US$66 million) per ship. Japan Marine United Corporation (JMU) is the prime contractor for this program with Mitsubishi Heavy Industries (MHI) chosen to be the subcontractor. Both JMU and MHI as well as Mitsui Engineering & Shipbuilding had submitted preliminary designs for the proposed next-generation OPVs.^[60][61]

Aegis system equipped ships (ASEV)

In 2020, Japanese Defense Minister Nobuo Kishi announced plans to build 2 new Aegis destroyers (pictured) to replace its scrapped land-based Aegis Ashore ballistic missile interceptors program.^[62] On August 31, 2022, the Japan Ministry of Defense announced that JMSDF will operate two "Aegis system equipped ships" (イージス・システム搭載艦 in Japanese) to replace its earlier cancellation of the Aegis Ashore program, commissioning one ship by the end of fiscal year 2027, and the other by the end of FY2028. The budget for design and other related expenses are to be submitted in the form of “item requests”, without specific amounts, and the initial procurement of the lead items are expected to clear legislation by FY2023. Construction is to begin in the following year of FY2024.^{[63][64][65][66]}

Amphibious assault ships (LHD)

In 2014, Japanese Defense Minister Itsunori Onodera expressed the intention of buying one amphibious assault ship (LHD) from the United States to provide more amphibious capabilities than the current Osumi class landing ships. The Wasp-class amphibious assault ship is most likely candidate for acquisition.^[68]

Amphibious transport dock (LPD)

At the Maritime Air Systems & Technologies (MAST) 2017 naval defense exhibition held in Tokyo, Mitsui Engineering & Shipbuilding (MES) unveiled a new amphibious transport dock (LPD) concept. According to Mistui spokesmen, the main missions of the proposed LPD vessel is island defense as well as humanitarian assistance/disaster relief (HA/DR) operations, with the Japan Maritime Self-Defense Force (JMSDF) is reportedly looking to boost its amphibious capabilities in order to protect its Southern Islands.^[73]

The proposed MES LPD design concept has an aft flight deck with two helicopter spots and a hangar large enough to receive two V-22 Osprey tilt-rotor aircraft and a small size VTOL unmanned aerial vehicle (UAV) similar in size to the MQ-8B Fire Scout. Beneath the flight deck is a well deck large enough to accommodate two Landing Craft Air Cushion (LCAC) hovercraft. Up to 40 AAV, MBT, and APC vehicles can be carried on two lower decks within the ship. The proposed ship measures 210 m (689 ft 0 in) in length, 30 m (98 ft 5 in) in width, and a draft of 7 m (23 ft 0 in) with a displacement of 16,000 long tons (16,000 t) and a speed of 22 kn (25 mph; 41 km/h). The maximum complement of the vessel is 200 people, including embarked troops. The LPD is fitted with a forward Phalanx CIWS gun mount and a SeaRAM launcher on top of the helicopter hangar. The vessel has two shafts and two rudders, as well as two bow thrusters, and also features two retractable fin stabilizers.^[73]

Mobile landing platform (MLP)

At the Maritime Air Systems & Technologies (MAST) 2017 naval defense exhibition held in Tokyo, Mitsui Engineering & Shipbuilding (MES) unveiled its Mobile Landing Platform (MLP) concept designed for large scale transportation of Landing Craft Air Cushion (LCAC) hovercraft, main battle tanks (MBTs), vehicles, cargo, and other equipment, with multi-mission and modular features. In addition to its aviation operations and amphibious capabilities, this MLP can act as an offshore base. The Japan Maritime Self-Defense Force is reportedly looking to boost its amphibious capabilities in order to protect its Southern Islands.^[74]

The MES's overall MLP design combines the aviation facilities of the U.S. Navy's Lewis B. Puller-class expeditionary mobile base ships with the extensive amphibious and expeditionary capabilities of the Montford Point-class expeditionary transfer dock vessels. There are four helicopter spots on the flight deck, but no helicopter hanger, with an elevator for stores and equipment next to spot #2. There is also a ramp allowing vehicles access between the two main decks. The MES mobile landing platform concept measures 240 m (787 ft 5 in) in length, 39 m (127 ft 11 in) in width, and a draft of 7 m (23 ft 0 in). The ship's displacement is 21,000 long tons (21,000 t), a speed of 15 kn (17 mph; 28 km/h), and a maximum complement of 240 people.^[74]

33DD destroyers

The 33DD (also known as DDR or Destroyer Revolution) was a Japanese destroyer proposed for the Japan Maritime Self-Defense Force. The tentative name of the class, 33 DD, is derived from an estimate that it would be budgeted in the Japanese era of Heisei 33 (2021).^[75][76]

High Speed Multi-hull Vessel Optimization (HSMVO)

The joint HSMVO research is conducted by the Acquisition, Technology & Logistics Agency (ATLA) and the Naval Surface Warfare Center Carderock Division of the US Navy.^[77][78] Also known as the Future Multi Purpose Trimaran concept, the HSMVO design concept is based on the Independence-class littoral combat ship with its distinctive trimaran hull design, modular mission capabilities, and aluminum construction (pictured). The mission capabilities of the concept includes mine countermeasure (MCM), humanitarian assistance and disaster recover (HADR), and offshore patrol/special ops. Likewise, each configuration will consist of different weapons, equipment, and supplies.^[78]

ATLA unveiled the HSMVO trimaran warship concept model at the Japanese defense trade-show MAST Asia 2017. According to Navy Recognition website, the project is set to end in 2018 and the JMSDF would ultimately decide whether to adopt the concept for development or not.^[78] To date, no decision has been made regarding the future acquisition and construction of warships based on the HSMVO design concept.