Since becoming the first princess from a non-imperial family when she was 24 years old, Empress Michiko said it was "not easy" by any means.

The empress, who raised her three children herself rather than leaving them to a foster mother, said parenting was "always a source of immense joy," adding it was "a constant battle against sleep."

It was a long custom in the imperial family to hire a foster mother but Crown Prince Naruhito and Crown Princess Masako are also raising their daughter Princess Aiko by themselves.

Answering a question from the press about what she wants to do after retiring from official duties, the empress said she wants to spend the rest of her days "peacefully" by her husband's side and read as many books as possible, especially detective novels.

"I have done my best to stay away from detective novels because I tend to get absorbed in them once I start reading, but I will no longer have to worry about having them near me," the empress said. "There are two or three P.J. Wodehouse "Jeeves" books waiting for me."

Looking back at the past year, the empress said she was saddened by a series of natural disasters, including torrential rains and earthquakes, which devastated many parts of Japan and overseas.

"I mourn with all my heart for the people who lost their lives to disasters across Japan and hope I can share, even in a small way, some of the sorrow of those left behind," she said.