Version 1 does not have a built-in language switcher in the settings menu. To change the interface from Japanese to English, you usually have to perform a "file swap."

If you purchased SAI directly from the official website (www.systemax.jp), you likely have the Japanese version by default. However, SYSTEMAX provides a separate English build for international customers.

You followed the steps, but SAI still looks like a foreign alphabet soup. Here is the diagnosis:

Before we get into the solutions, you need to understand why this is so difficult.

Paint Tool SAI was developed by a small Japanese company, SYSTEMAX. Originally, the software was designed exclusively for the Japanese market. The "English version" is technically a separate build. When you install SAI, the language is hard-coded into the executable (.exe) file.

Crucial fact: There is no Language folder. There are no .po or .mo translation files. You cannot press Ctrl+K and select "Français."

To change the language, you must physically replace the core program files or change your system’s Unicode settings.

Most users looking for "paint tool sai change language" are using SAI Ver. 1 (the classic version with the grey interface). Over the years, fan-made repacks (like SAI 1.2.5) have included multiple languages hidden in the installation folder.

Here is the most common fix for SAI Ver. 1: