[1] "Taro (太郎)" was named by Kazunori Ukigawa (浮川 和宣), a founder of JustSystems.

[2] Sanyo Electric already had a trademark right of the name,[3] so JustSystems added a prefix "Ichi (一)" as they hoped the software won the best.

[4] JustSystems was founded in July 1979 by Hatsuko (初子) and Kazunori Ukigawa, and was incorporated in June 1981.

Toshiba released JW-10 [ja] in February 1979, the first word processor for the Japanese language, but it sold less than their business computers.

He founded the company as a dealer of business computers, and they started selling Japanese language software.

JS-WORD featured mouse support and a graphical icon-based interface, but it resulted in poor performance.

[6] The biggest competitor, Matsu (松), was released in 1983 by Kanri Kōgaku Kenkyūjo (管理工学研究所).

It gained speed from being written in assembly language and natively ran on PC-9801, but Matsu's Japanese input method couldn't be used for other applications.

[6] Contrary to the Japanese personal computer market expanding into beginners, Matsu oriented for power users, so Ichitaro overtook it.

As of 1997, a Japanese media website reported that 64% of readers using Microsoft Word, and the main reason was that they used it in offices and schools.

On 1 February 2005, sales and production of the software were frozen pending an appeal by the company against a ruling of the Tokyo District Court which states that there is a breach of a patent owned by Matsushita Electric Industrial Co., Ltd.[15] However, on 30 September 2005, Intellectual Property High Court of Japan, which was newly formed in April 2005, has granted JustSystems’ appeal.

In the 2010s, they focus on correspondence education and enterprise software although Ichitaro and ATOK continue to be developed.