SEOUL, South Korea (AP) — This week's summit between rivals North and South Korea represents, in part, unfinished business for South Korean President Moon Jae-in.

In pursuing engagement with North Korean leader Kim Jong Un to defuse a nuclear crisis, Moon is also looking to bolster the legacy of his late friend and political mentor, former President Roh Moo-hyun, whose ambitious efforts to build trust with North Korea crumbled as it began building its nuclear arsenal a decade ago.

A dovish liberal, Moon said he will use the meetings with Kim in Pyongyang, North Korea's capital, which began Tue...