TOKYO -- When Miho Otani was a college student, she felt the urge to change her "lukewarm" life. Now she is tasked with defending Japanese waters at a time when regional tensions are heating up.

Otani is a Maritime Self-Defense Force commander. In February, she became the first female captain of a Japanese destroyer. On the missile- and torpedo-equipped Yamagiri, Otani and her crew of 200 are responsible for guarding against intrusions by foreign vessels.

Miho Otani

The threat was underscored in early June, when a Chinese naval ship entered a contiguous zone bordering Japan's territorial waters near the Senkaku Islands in the East China Sea. Beijing claims the uninhabited islets, which it calls Diaoyu.

As a skipper, the 45-year-old finds shut-eye is hard to come by. "I don't get enough sleep, as I receive reports day and night," she said with a smile, sitting in the captain's seat on the Yamagiri's bridge.

A mother at sea

It was after watching coverage of the Gulf War that Otani decided to leave college to pursue her calling. She went on to graduate from the National Defense Academy of Japan in 1996 -- one of the first women to do so.

After joining the MSDF, she was assigned to duty afloat for more than a month at a time. This was no small sacrifice: As a divorced mother, Otani had no choice but to ask her parents to look after her daughter for long stretches.

"My daughter grew out of diapers and started talking before I knew it," she said.

When her daughter was in elementary school, Otani was assigned to sea for six months. In explaining why she would be away for so long, she told her daughter, "I need to take this assignment to become a destroyer captain."

Her daughter is now in junior high school, and stays in a dorm. When Otani became a captain, her daughter said she was happy that her mother's dream had come true.

More than 90% of SDF officials are men, but Otani said she no longer feels discrimination. Still, she does feel pressure to perform well, to help ensure that other women get similar opportunities. In her view, when it comes to national defense, there is no distinction between men and women.