It’s the end of an era for Komeito, the ruling Liberal Democratic Party's coalition partner. On Tuesday, Natsuo Yamaguchi announced that after 15 years at the helm, he would not seek reelection in his party's Sept. 28 presidential election.

The 72-year-old Yamaguchi, first elected as party leader in 2009, is expected to be replaced by 66-year-old Secretary-General Keiichi Ishii, the only candidate in the race. Ishii will be formally chosen by the party at its convention later this month, one day after the LDP's presidential race, which will also effectively decide who the next prime minister will be.

Attention now turns to how Yamaguchi’s exit and Ishii’s ascent could impact the LDP race, with a focus on who among the LDP candidates might be best placed to work with Komeito. For his part, Yamaguchi said he wanted the ruling coalition to continue to cooperate despite some differences, and that the leaders of the LDP and Komeito needed to be in tune with each other.