If you hold a passport from a visa exempt country, this doesn’t apply to you:

https://www.mofa.go.jp/j_info/visit/visa/short/novisa.html

But if you don’t have a passport from that list, you do need a visa.  Unfortunately, the change of government in Japan has made the process for getting a visa more taxing on the body supplying the invitation letter (in our case, the Linux Foundation).  For this reason, the LF is insisting that anyone who needs a visa letter have their application in to the LF dashboard by 17 November at the latest:

https://openprofile.dev/myevents?applyfor=visa-letter

If you have any queries or problems with the process, please contact visaletters@linuxfoundation.org