Facing reprisals from Beijing for a remark over Taiwan, Prime Minister Sanae Takaichi must walk a fine line to prevent escalating the dispute without looking weak at home.

Taiwan President Lai Ching-te showed his support for Japan on Thursday with a lunch of Japanese-sourced sushi, after China indicated it would ban all imports of the country's seafood in an escalating dispute over the Chinese-claimed island. Tensions between the two countries ignited after new Japanese Prime Minister Sanae Takaichi…