Japan has a very similar politcal system to the U.K. – two main parties, upper and lower houses and a Prime Minister.
The current Japanese prime minister is Shinzo Abe.
He’s been leading Japan since 2012.
The Prime Minister title is 内閣 総理 大臣 in Japanese.
It’s read as naikaku souri daijin.
People often refer to the PM as 首相・しゅしょう – shusou.
Abe’s the leader of of the ruling party – the LDP (Liberal Democratic Party) of Japan.
A surprising fact I learned about him is that he was already Prime Minister between 2006-2007.
In Japan there is no restriction on how many times or for how long you can be prime minister.
If you’re interested wikipedia is a good place to start!