Emperor Akihito's retirement will be the first imperial abdication in more than two centuries.
Tokyo is eyeing the end of 2018 as a likely timeline for his retirement, Japanese media said.
"I would like to give my whole heart and soul to every duty, including official duties I have already inherited from His Majesty," Crown Prince Naruhito told reporters, according to Kyodo News.
Asked about the enactment of the law, the crown prince said he would refrain from commenting on it.
The popular 83-year-old monarch shocked the country last summer when he signalled his desire to take a back seat after nearly three decades on the throne, citing his age and health problems.
The unexpected move presented a challenge since there was no law to deal with an emperor retiring from what is usually a job for life -- and it reignited debate about allowing women to ascend the male-only throne.
There are no more eligible male heirs after the 10-year-old son of Crown Prince Naruhito's younger brother Akishino.
There have been abdications in Japan's long imperial history, but the last one was more than 200 years ago, so politicians had to craft new legislation to make it possible.
Naruhito visits Denmark Thursday to commemorate 150 years of diplomatic ties between the two countries.
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