The nation might soon see either its first female or youngest-ever head of government while the nation's governing faction votes for its second new leader in just over twelve months.
The Liberal Democratic Party is looking to replace the outgoing head of government, who stepped down last month after his government failed to maintain control across both chambers of parliament.
The successful candidate will face various difficulties - including leading a party still struggling to regain voter trust after major economic misconduct controversies.
They will also need to balance the tense American-Japanese ties and executing the trade agreement established by the Ishiba government with the former US leadership.
A planned meeting by Trump to Japan in late October comes as the two countries - long-standing partners and major partners on economic and defense matters - persist in working out how to implement the deal over tariffs.
Within the country, the new leader will also have to find a way to boost the struggling economic situation and deal with rising inflation and a persistent living expense emergency, on top of countering a movement in the direction of conservative extremism.
Securing the position of head of government for the victor cannot be assumed since the ruling party no longer holds complete control within the legislature.
This weekend's selection will occur among the LDP's 295 parliamentarians along with local supporters.
Should no candidate secure the required votes during the first round, a second ballot will quickly follow between the top two candidates.
Multiple candidates remain in contention as frontrunners: the agriculture minister, Yoshimasa Hayashi, and Sanae Takaichi, who would be Japan's first female prime minister if she won.
The female candidate, in her mid-sixties, is a long-time admirer of Margaret Thatcher's leadership.
Known as a close ally and protégé of the former leader, she represents a hardline conservative, publicly rejects marriage equality and has regularly visited the disputed memorial site.
Previously not considered a strong advocate regarding gender equality, however her position has shifted recently, pledging to make childcare costs eligible for tax benefits and proposing business incentives for companies offering workplace daycare facilities.
She has promised to double the size of the economy in a decade with heavy state investment for innovative developments, public works, food production along with additional fields ensuring financial stability.
The younger candidate, 44, follows in the footsteps of his political father, the former leader during the early 2000s.
Considered the young fresh-face of the mostly older LDP, Koizumi engages well with press and popular on social media, recognized for posting cat photos.
Public support increased recently as agriculture minister after reducing costs for staple foods while receiving acclaim from party elders for his leadership on the issue.
Similar to competitors, the minister promised to trim taxes to help households cope with rising living costs.
Another leading candidate is 64-year-old Hayashi, who is also the official administration representative.
Analysts note he's "someone who is a more reserved figure, but experienced and tested.
Many of Hayashi's supporters hail from a faction previously headed by the ex-leader.
Additional candidates under consideration include former foreign minister Toshimitsu Motegi along with the previous economic official Takayuki Kobayashi.
This political contest follows a bruising few years for the ruling faction which saw a "cascade" of scandals, widespread voter apathy historically poor polling numbers.
Earlier this year, the incoming leader announced a snap election during autumn, saying it was crucial for fresh leadership to be judged by the people as soon as possible.
It was a political gamble that backfired.
Voters - angry about misconduct allegations and struggling to deal with price increases and a cost-of-living crisis - returned the party's worst result for ten years.
Since over a decade ago, the LDP - governing the nation almost continuously for decades - lost its parliamentary majority.
Then this year, control diminished during senate voting.
The leader initially declined requests for resignation at first, saying he needed to accept accountability for the LDP's losses and to deal with international agreements.
However recently - before party elections that would've likely voted him out - he resigned, announcing his resignation and setting the stage for today's vote.
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