They are also three of about 40 women in their 2,400-person unit.
Living alongside a close-knit group of other female service members aboard the JS Osumi, a Japanese Maritime Self-Defense Force tank landing ship deployed for exercises in the East China Sea, they in November supported beach assault drills in Japan's vulnerable southwest island chain.
Although they and their fellow marines are expected to lead the way on the frontlines, their unit - and Japan's military - lag far behind in gender diversity, a problem that risks turning into a crisis as the country's greying population shrinks while threats from China, Russia and North Korea grow.
"Women are crucial to ensuring a stable supply of suitable recruits," Shingo Nashinoki, then-commander of the ARDB force, said on an uninhabited island in the Okinawan chain, where a small all-male ARDB contingent practiced helicopter attacks.
WOMEN WANTED
Although the number of Japanese female soldiers has doubled during the past decade, it is still far behind Tokyo's ally, the United States.
Women make up only 8.7% of the 230,000 strong Japanese Self-Defense Forces (JSDF), half the rate of the U.S. military, and only 1.6% of the ARDB, which was activated in 2018. That compares with the almost one in ten U.S. Marines who are women.
"The ARDB has a reputation for being physically, mentally, and technically demanding, and I think that a lot of women worry whether they could handle that," Staff Sergeant Maruyama, 38, a medic, said in the amphibious landing ship's mess hall.
Aboard the Osumi, women are uncommon. Only men participated in a fitness training session on the flight deck. Maruyama and Corporal Kurosawa, 20, instead stretched in the ship's small gym while male colleagues around them lifted weights.
CHALLENGES
The SDF's efforts to present itself as a more female-friendly force have been undermined in recent months by high-profile sexual harassment cases.
In October, Minister of Defence Minoru Kihara had to apologise after a Japanese sailor was forced to meet a superior accused of sexually harassing her. In December, a Japanese court found three male soldiers guilty of sexually assaulting a female comrade.
"It leaves me a bit speechless. It's important to be clear to every person what harassment is and to continue educating people," said Captain Nakano, 42, aboard a ship that was not designed to accommodate a mixed-gender crew when it was commissioned two decades ago, before she joined. She would like to see more roles opened to women, she added.
Maruyama, who has two daughters with her SDF-enlisted husband, says more childcare help would be a boon.
"The reality is that women are expected to be more involved in raising their children," she said.
Unlike male military personnel, who sleep in bunks assigned to them by rank and unit, the three female marines are billeted together with other women in cabins near the ship's bow regardless of rank. The men onboard are warned to stay away from the area.
Accommodations are cramped for everyone, with three-tier bunk beds separated by narrow aisles filled with bags, suitcases and small camping stools that soldiers and sailors bring from home.
Kurosawa, who joined the ARDB less than two years ago, likes having older female colleagues close by that she can confide in.
"There aren't many women in the military, and it's important to be able to find someone to talk to," said Kurosawa, a mechanic who maintains the ARDB's trucks on the ship's vehicle deck.
Above the washing machines nearby that line one side of that compartment, the men hang their uniforms and underwear to dry.
