Hi,
There is a bad bug in the tutorial for Japanese. When you get to the part where you're supposed to drag a character from the "leave behind" area to the top area, the text in Japanese instead tells you to click the random button. But when you click the random button it just shows an error like "hey, you have to click the random button first!" (which exactly is what you just did)
I couldn't figure what to do without changing it to English.
Thank you for the reporting this.
Although the translations for the game are all community based, so if this is just a translation error, which it sounds like it is (as opposed to some text that was untranslatable due to the game coding), then all the developers can do is mention it to those kindly volunteering their help with the Japanese translation project (since I'm pretty sure none of the developers knows Japanese).
In which case translation errors is also something players can report/fix themselves rather than relying on the developers to do it. Either by contributing to the translation project themselves (fix). Or by just leaving a message for those who are volunteering (report), and ideally highlighting the current translation error, and offering a suggesting regarding an alternative / correct translation.
At this point I would normally point you in the direction of the official Japanese translation thread on this forum, but the thread looks very dead (last post June 2014). https://ludeon.com/forums/index.php?topic=4030.0 . Although if you do wish to contribute to the project then there's nothing wrong with you resurrecting that thread. The project itself looks alive and well though, with the last edit being less than a month ago. https://github.com/Ludeon/RimWorld-ja
I do not know much about GitHub, but there's a comment section on the above page (51 comments at the moment), so you should be able to leave a message about this there (if you wish).