North Korea has been preparing a succession contingency plan since late last year in which power would transfer from Kim Jong-un to his younger sister, according to the Yomiuri Shimbun.

The Japanese newspaper made the report on Wednesday, quoting a source familiar with trilateral discussions involving South Korea, the U.S. and Japan. 

The report said the plenary meeting of the North Korean Workers’ Party central committee late last year made an internal decision that should Kim Jong-un not be able to govern the country due to death or other reasons, all power will be given to Kim Yo-jong. 

The source said since then many orders under Kim Yo-jong’s name have been delivered to the party and the military. 

Kim Yo-jong, who serves as the first vice department director of the Workers’ Party Central Committee, studied in Switzerland with her brother and is known to be his most trusted aide and the second most powerful person in the regime. 

The sister issued her first official statement last month, delivering the country’s messages to South Korea and the U.S. 

The Yomiuri report came a day after CNN said the U.S. is monitoring intelligence that Kim Jong-un is in grave danger after undergoing surgery, stoking suspicions about the secretive leader’s health condition. 

Yomiuri said Kim could be suffering from worsening complications with hypertension, diabetes and heart disorders, as a rumor is spreading that a group of French doctors visited the North in January to treat him.