Originally Posted by Rebafan81
Quick question regarding Naruhito becoming Emperor, could he change the succession law so that his daughter was next in line when he becomes Emperor?
No. The Japanese Constitution, drafted by the United States and the other Allied Powers after Japan's defeat in WWII, gives the Emperor zero comma zero political influence. Even the Address by Emperor Akihito is met with such caution and care, as the Japanese Government and the Imperial Household Agency are painfully maintaining the Emperor's total non-influence as a dogma.
This was the prize the monarchy had to pay after the total defeat in WWII. Being ceremonial puppets but remaining an imperial family with all privileges, or the downfall of the monarchy (like happened in China, think about the movie The Last Emperor) and a prosecution of Emperor Hirohito and other members of the imperial family for war crimes and crimes against humanity.
If there is any desire to make Princess Aiko an Empress, it has to come from the Prime Minister and the Diet (Parliament). The current Prime Minister is a conservative with an overwhelming majority in Parliament, most likely unwilling to change the status-quo since there are heirs enough: Prince Naruhito, his brother Prince Akishino, his nephew Prince Hisahito, etc.