KASHIWA, Japan — Maria Fransiska, a young, hard-working nurse from Indonesia, is just the kind of worker Japan would seem to need to replenish its aging work force.

But Ms. Fransiska, 26, is having to fight to stay. To extend her three-year stint at a hospital outside Tokyo, she must pass a standardized nursing exam administered in Japanese, a test so difficult that only 3 of the 600 nurses brought here from Indonesia and the Philippines since 2007 have passed.

So Ms. Fransiska spends eight hours in Japanese language drills, on top of her day job at the hospital. Her dictionary is dog-eared from countless queries, but she is determined: her starting salary of $2,400 a month was 10 times what she could earn back home. If she fails, she will never be allowed to return to Japan on the same program again.

“I think I have something to contribute here,” Ms. Fransiska said during a recent visit, spooning mouthfuls of rice and vegetables into the mouth of Heiichi Matsumaru, an 80-year-old patient recovering from a stroke. “If I could, I would stay here long-term, but it is not so easy.”