Hanroku Yamaguchi’s “Plan for Osaka” is known to be a pioneering example of Japanese planning. This is the first in a series of papers confirming the contents of the accompanying text to Yamaguchi’s plan, “Explanation of the Plan for Osaka” by comparing two existing versions. Through close examination of the corrections made between versions, this study draws attention to city design topics that Yamaguchi was especially concerned about. Part one addresses the development of Yamaguchi’s street plan, from the city authority’s street design requirements, to the comprehensive consideration of city planning including other facilities and upgrading of the existing streets.