mozc_emacs_helper: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/mozc_emacs_helper - from package: emacs-mozc-bin

You may install the required package with command apt-get install {package}

Error in other languages:
mozc_emacs_helper: bevel nie gevind nie
mozc_emacs_helper: comandă negăsită
mozc_emacs_helper: comando não encontrado
mozc_emacs_helper: commande introuvable
mozc_emacs_helper: command not found
mozc_emacs_helper: käsku ei ole
mozc_emacs_helper: không tìm thấy lệnh
mozc_emacs_helper: komanda nerasta
mozc_emacs_helper: Kommando nicht gefunden.
mozc_emacs_helper: kommandot finns inte
mozc_emacs_helper: komut yok
mozc_emacs_helper: nie znaleziono polecenia
mozc_emacs_helper: níor aimsíodh an t-ordú
mozc_emacs_helper: no se encontró la orden
mozc_emacs_helper: no s'ha trobat l'ordre
mozc_emacs_helper: opdracht niet gevonden
mozc_emacs_helper: parancs nem található
mozc_emacs_helper: perintah tidak ditemukan
mozc_emacs_helper: príkaz nenájdený
mozc_emacs_helper: příkaz nenalezen
mozc_emacs_helper: команда не найдена
mozc_emacs_helper: командата не е открита
mozc_emacs_helper: 命令找不到
mozc_emacs_helper: コマンドが見つかりません