Thank you very much for your reply.
I have not fully understood it yet, can I install plasma-l10n?
Specifically, what kind of contents should I execute?

You already have plasma-l10n, on your next update (pacman -Syu) you will get a new version containing Japanese (wait a few hours though, not up yet).

EDIT:
New plasma-l10n is up in the build repo, you can install now with:

sudo pacman -U http://kaosx.tk/repo/build/plasma-l10n-5.8.4-2-x86_64.pkg.tar.xz

Thanks a lot demm.

Japanese was displayed in "Available Languages" of "Language-System Settings".
Thank you very much.
https://cdn.scrot.moe/images/2016/11/26/2016-11-26_11h25_29.png

I set as follows.

user $ sudo nano ~/.xprofile
export XMODIFIERS=@im=fcitx
export XMODIFIER=@im=fcitx
export GTK_IM_MODULE=fcitx
export QT_IM_MODULE=fcitx
export DefaultIMModule=fcitx

I can input Japanese.
https://cdn.scrot.moe/images/2016/11/26/2016-11-26_11h20_23.png

However,I get an error message.
https://cdn.scrot.moe/images/2016/11/26/2016-11-26_11h19_11.png

kactivitymanagerd-20161126-111237.kcrash

Application: kactivitymanagerd (kactivitymanagerd), signal: Segmentation fault
Using host libthread_db library "/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f71c9832800 (LWP 555))]

Thread 2 (Thread 0x7f71b0633700 (LWP 573)):
[KCrash Handler]
#5  0x00007f71afb91800 in ?? ()
#6  0x00007f71c7f47982 in QInternal::activateCallbacks(QInternal::Callback, void**) () from /usr/lib/libQt5Core.so.5
#7  0x00007f71c812c1e5 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib/libQt5Core.so.5
#8  0x00007f71c815c886 in QObjectPrivate::setParent_helper(QObject*) () from /usr/lib/libQt5Core.so.5
#9  0x00007f71c815ce38 in QObject::~QObject() () from /usr/lib/libQt5Core.so.5
#10 0x00007f71c8161899 in QSocketNotifier::~QSocketNotifier() () from /usr/lib/libQt5Core.so.5
#11 0x00007f71c98fa9ef in ?? () from /usr/lib/libQt5DBus.so.5
#12 0x00007f71c63c53b3 in _dbus_watch_list_remove_watch () from /usr/lib/libdbus-1.so.3
#13 0x00007f71c63c393e in ?? () from /usr/lib/libdbus-1.so.3
#14 0x00007f71c63c39b9 in ?? () from /usr/lib/libdbus-1.so.3
#15 0x00007f71c63c27fb in ?? () from /usr/lib/libdbus-1.so.3
#16 0x00007f71c63ae132 in ?? () from /usr/lib/libdbus-1.so.3
#17 0x00007f71c98ffe0b in ?? () from /usr/lib/libQt5DBus.so.5
#18 0x00007f71c98fff94 in ?? () from /usr/lib/libQt5DBus.so.5
#19 0x00007f71c9900299 in ?? () from /usr/lib/libQt5DBus.so.5
#20 0x00007f71c98ed7de in ?? () from /usr/lib/libQt5DBus.so.5
#21 0x00007f71c7f64049 in ?? () from /usr/lib/libQt5Core.so.5
#22 0x00007f71c68f4424 in start_thread () from /lib/libpthread.so.0
#23 0x00007f71c7880cad in clone () from /lib/libc.so.6

Thread 1 (Thread 0x7f71c9832800 (LWP 555)):
#0  0x00007f71c68fa03f in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#1  0x00007f71c7f64e3b in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/libQt5Core.so.5
#2  0x00007f71c7f63c36 in QThread::wait(unsigned long) () from /usr/lib/libQt5Core.so.5
#3  0x00007f71c98ed596 in ?? () from /usr/lib/libQt5DBus.so.5
#4  0x00007f71c98ed629 in ?? () from /usr/lib/libQt5DBus.so.5
#5  0x00007f71c77cec38 in __run_exit_handlers () from /lib/libc.so.6
#6  0x00007f71c77cec85 in exit () from /lib/libc.so.6
#7  0x00007f71c77b9717 in __libc_start_main () from /lib/libc.so.6
#8  0x00000000004090a9 in _start ()

I am sorry that I do not know how to use "code tags".

This problem could not be solved.
Thank you very much.

I just wanted to say that I have Japanese input working with both anthy and mocz.
My ~/.xpofile looks like this:

export QT_IM_MODULE=fcitx
export XMODIFIERS="@im=fcitx"

And my ~/.config/plasma-localerc looks like this:

[Formats]
LANG=ja_JP.UTF-8

[Translations]
LANGUAGE=en_US

With only en_US.UTF-8 and ja_JP.UTF-8 uncommented in /etc/locale.gen (and generated)

I don't know if this has anything to do with this, but I thought I'd add it just in case.
I'd be happy to help if needed.

Thanks a lot photodiode.

I set as follows.

user $ cat ~/.xprofile
export QT_IM_MODULE=fcitx
export XMODIFIERS="@im=fcitx"

user $ cat ~/.config/plasma-localerc
[Formats]
LANG=ja_JP.UTF-8
LC_COLLATE=ja_JP.UTF-8
LC_MEASUREMENT=ja_JP.UTF-8
LC_MONETARY=ja_JP.UTF-8
LC_NUMERIC=ja_JP.UTF-8
LC_TIME=ja_JP.UTF-8
useDetailed=true

[Translations]
LANGUAGE=en_US

With only en_US.UTF-8 and ja_JP.UTF-8 uncommented in /etc/locale.gen (and generated)
https://cdn.scrot.moe/images/2016/11/27/2016-11-27_19h27_54.png

I can input Japanese.
https://cdn.scrot.moe/images/2016/11/28/2016-11-28_09h23_10.png

However,I get an error message.
https://cdn.scrot.moe/images/2016/11/27/2016-11-27_18h07_28.png

kactivitymanagerd-20161127-180534.kcrash
Application: kactivitymanagerd (kactivitymanagerd), signal: Segmentation fault
Using host libthread_db library "/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7feed608f800 (LWP 540))]

Thread 2 (Thread 0x7feebce0d700 (LWP 553)):
[KCrash Handler]
#5 0x00007feebc39f800 in ?? ()
#6 0x00007feed47a4982 in QInternal::activateCallbacks(QInternal::Callback, void**) () from /usr/lib/libQt5Core.so.5
#7 0x00007feed49891e5 in QCoreApplication::notifyInternal2(QObject, QEvent) () from /usr/lib/libQt5Core.so.5
#8 0x00007feed49b9886 in QObjectPrivate::setParent_helper(QObject*) () from /usr/lib/libQt5Core.so.5
#9 0x00007feed49b9e38 in QObject::~QObject() () from /usr/lib/libQt5Core.so.5
#10 0x00007feed49be899 in QSocketNotifier::~QSocketNotifier() () from /usr/lib/libQt5Core.so.5
#11 0x00007feed61579ef in ?? () from /usr/lib/libQt5DBus.so.5
#12 0x00007feed2c223b3 in _dbus_watch_list_remove_watch () from /usr/lib/libdbus-1.so.3
#13 0x00007feed2c2093e in ?? () from /usr/lib/libdbus-1.so.3
#14 0x00007feed2c209b9 in ?? () from /usr/lib/libdbus-1.so.3
#15 0x00007feed2c1f7fb in ?? () from /usr/lib/libdbus-1.so.3
#16 0x00007feed2c0b132 in ?? () from /usr/lib/libdbus-1.so.3
#17 0x00007feed615ce0b in ?? () from /usr/lib/libQt5DBus.so.5
#18 0x00007feed615cf94 in ?? () from /usr/lib/libQt5DBus.so.5
#19 0x00007feed615d299 in ?? () from /usr/lib/libQt5DBus.so.5
#20 0x00007feed614a7de in ?? () from /usr/lib/libQt5DBus.so.5
#21 0x00007feed47c1049 in ?? () from /usr/lib/libQt5Core.so.5
#22 0x00007feed3151424 in start_thread () from /lib/libpthread.so.0
#23 0x00007feed40ddcad in clone () from /lib/libc.so.6

Thread 1 (Thread 0x7feed608f800 (LWP 540)):
#0 0x00007feed315703f in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#1 0x00007feed47c1e3b in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/libQt5Core.so.5
#2 0x00007feed47c0c36 in QThread::wait(unsigned long) () from /usr/lib/libQt5Core.so.5
#3 0x00007feed614a596 in ?? () from /usr/lib/libQt5DBus.so.5
#4 0x00007feed614a629 in ?? () from /usr/lib/libQt5DBus.so.5
#5 0x00007feed402bc38 in run_exit_handlers () from /lib/libc.so.6
#6 0x00007feed402bc85 in exit () from /lib/libc.so.6
#7 0x00007feed4016717 in
libc_start_main () from /lib/libc.so.6
#8 0x00000000004090a9 in _start ()
I am sorry that I do not know how to use "code tags".

When I create "~/.bashrc file" and "~/.xprofile file", I get an error message.

Is there a way to solve this problem?
I am in trouble because a lot of error messages came out.
Could you tell me the professor, please?
Thank you very much.

Sorry, it's hard to say what could be wrong (if anything)..

When exactly does the error appear?
Is it when you confirm a word, or just randomly?
Also I see that you have updates in the screenshots, is your system up to date?

Thanks a lot photodiode.

Thanks for your advice.
This problem is very difficult for me.
I'd like to close this thread.
Many thanks.

Before stopping to figure this issue, please post the contents of /etc/locale.conf

Contents of /etc/locale.conf are as follows.

user $ cat /etc/locale.conf
LC_ADDRESS=ja_JP.UTF-8
LC_IDENTIFICATION=ja_JP.UTF-8
LC_TIME=ja_JP.UTF-8
LC_PAPER=ja_JP.UTF-8
LANG=ja_JP.UTF-8
LC_MEASUREMENT=ja_JP.UTF-8
LC_MONETARY=ja_JP.UTF-8
LC_NAME=ja_JP.UTF-8
LC_NUMERIC=ja_JP.UTF-8
LC_TELEPHONE=ja_JP.UTF-8

@photodiode can you compare that locale.conf to what you have? Calamares, the installer, recently changed to this format so you might not have this.

    What exactly is that I have?
    I updated the system.

    Contents of ~/.config/plasma-localerc are as folloes.

    user $ cat ~/.config/plasma-localerc
    [Formats]
    LANG=ja_JP.UTF-8
    LC_COLLATE=ja_JP.UTF-8
    LC_MEASUREMENT=ja_JP.UTF-8
    LC_MONETARY=ja_JP.UTF-8
    LC_NUMERIC=ja_JP.UTF-8
    LC_TIME=ja_JP.UTF-8
    useDetailed=true
    
    [Translations]
    LANGUAGE=ja
    • demm replied to this.

      enpitu please add code tags, I've been doing it for you so far, but it really is simple to do. Either enclose code with 3 back ticks (```) or use the editor menu and click on "Code".
      And if you still don't understand, just "edit" one of your posts, you see how the code tags are added.

      Thanks a lot demm.

      I use "KaOSx KDE" as the very beautiful "Linux OS" of the English version.

      demm Mine is almost completely empty

      $ cat /etc/locale.conf
      LANG=