How is the prime minister elected?

The Japanese prime minister is chosen by the Diet, but not everyone can run for prime minister.
Because of the nature of the Jaanese government, which is party-based, a candidate for prime minister must be a member of the Diet.
And he or she must be a civilian. (Actually, all Japanese are civilians since there is no formal military in Japan.)
Political parlies, independent and coalition alike, recommend the presidents or leaders of their parties for the position of prime minister, in hopes of increasing their power.
The fight for power among parties is so heated that emphasis is often placed on their self-interest rather than on the interests of the people.
There is always a fear of monev politics being the name of the game.
The fact that most people in Japan feel somewhat isolated from actual politics may stem from the way the prime minister is chosen.