The last version personally published by Mitsuyoshi was the Idai (井大), which came out in the eighteenth year of the Kan'ei (1634).

[4] The name Jinkōki is derived from jintenkō (塵点劫), an immeasurably long span of time mentioned in the Lotus Sutra, hence the nuance of permanence in the Sino-Japanese word jinkō and its reflection in English title.

[4] The book contained instructions for dividing and multiplying with a soroban and mathematical problems relevant to merchants and craftsmen.

[6] In addition to fundamental knowledge such as numerical notation, units, and multiplication tables, it also included slightly more specialised topics, such as methods to find square roots and cube roots, practical calculations of area, currency conversion, and interest calculation.

The content covers almost all arithmetic needed in daily life at that time, and it is a characteristic of the book that explanations are given using familiar topics, such as using the increase of mice as an example for geometric progression.