CHANGCHUN, China—When this industrial city was the capital of the Japanese kingdom of Manchukuo in the 1930s and ‘40s, it was an urban wonder.

Changchun was the masterpiece of Nobusuke Kishi, the grandfather of Japan’s Prime Minister Shinzo Abe. The chief industrial planner of Manchukuo, Mr. Kishi was a brilliant technocrat who transformed a vast wilderness north of the Great Wall into an industrial behemoth.

That fact, in today’s China, is an embarrassment—a painful one given how Beijing has stressed Japan’s brutal wartime occupation, and reviled the administration of Mr. Kishi’s grandson.

There are many good reasons Mr. Abe’s sweeping electoral victory on Sunday should improve a relationship that has been haunted by bitterly contested views of wartime history.

From Beijing’s point of view, there’s now no avoiding Mr. Abe. Japanese voters have given him a fresh four-year mandate, so waiting him out is no longer a viable option.