Japan exists.
I implement Japanese input support via:
I recommend the ArchWiki article ⇗ as a guide.
On Gentoo in particular, LTO compilations come with recommendations to change some warnings into errors ⇗. One of fcitx's compile-time warnings becomes such an error. For safety, I disable its LTO via package.env below.
See the make.conf ⟹ article on the environment no-lto is referencing).
/etc/portage/package.use/inputmethod
app-i18n/mozc fcitx5
/etc/portage/package.accept_keywords/inputmethod
app-i18n/mozc ~amd64
/etc/portage/package.env/no-lto
app-i18n/fcitx no-lto
Once you set up autostart for fcitx5, it's a mere CTRL+SPACE to toggle input methods. I think.
Characters may be garbled when unzipping downloaded .zip files; in this case, we need to Japanify the unzipping. AskUbuntu ⇗
/etc/portage/package.use/random-libs
app-arch/unzip natspec
/etc/locale.gen
... (previous stuff)
ja_JP.UTF-8 UTF-8
... (next stuff)
Then merely extract some Japanese zip file like so:
LANG=ja_JP.UTF-8 unzip ばか.zip