The nation set to elect female prime minister in landmark first

Over the last two decades, the country has had more than 10 leaders.

Actually, one expert likens assuming the nation's top job to drinking from a "poisoned chalice".

However, what is the reason does the country keep changing prime ministers? It's due in part of it being a "one-party democracy", says Prof James Brown of Temple University Japan.

The Liberal Democratic Party's control on the political landscape means the main political competition originates within the party, instead of from external parties.

"Therefore inside the LDP there are intense conflicts within various groups - they all desire their own clique to get the leadership position."

"Thus although you might be chosen as prime minister, as soon as you're in power, you have dozens of people scheming to try to remove you again."

Key Factors Behind Frequent Changes

• Single-party rule restricts outside challenges
• Party infighting drive leadership contests
• The leadership role is often described as a "cursed position"
• Government continuity remains elusive despite financial power