Update: Aug 29, 2017. I did "root" the 2nd time. (for two different devices.)

1st time: EMUI 4.1. twrp-3.02. supersu-2.76.
2nd time: EMUI 3.1. twrp-3.02. supersu-2.82.

1. Preface
I wanted to delete the shutter sound of Camera App. My Huawei is from Japan. Japan Model can not silence the sound. I just wanted to perform this command: rm /system/media/audio/ui/camera_click.ogg. It can not be performed without root permission.
2. Easier ways did NOT Work!
I tried these easier ways but These did not work!
• Kingoroot App: tried many times with no success.
• Kingoroot PC : tried many times with no success.
• Towelroot: tried many times with no success.

If one of these worked, it would be better, since they are just "a couple of clicks away" things. But they did not work unfortunately. So I needed to try a harder way.

3. Preparation
• Enable Developper mode on your mobile
1. Go to Setup(Application)->system->Terminal Infomation(very bottom).
2. Tap 5 times on Build Number
3. Developper mode Enabled now.
4. Go to Setup(Application)->system->Developper's options(now appeared).
5. "USB Debug" on.
6. "OEM unLock" on. (you need your pwd to turn it on.)
   "FRP unlock"ed
• Set up your computer to connect with your mobile
1. You need adb and fastboot.
You can download them many places. In my case they were installed when Android studio was installed.
2. They were run from shell, so add the path.
C:\Users\User_name\AppData\Local\Android\sdk\platform-tools. In case of Windows 10, you have to add a ps1 file in c:/Users/User_name/Documents/WindowsPowerShell/.
3. set ps1 runnable on powershell in case of Windows10.

   > Set-ExecutionPolicy -ExecutionPolicy unrestricted -scope currentuser
   

4. Check adb run properly by adb devices

>adb devices
List of devices attached
KIIL22XXXXXXX device

Your device ID is shown? then go ahead.
4. Unlock bootloader
Tips: English webpage for unlock password is not found. But Chinese language page is available. Use with google translate! It would be not so hard. http://www.stechguide.com/unlock-bootloader-of-huawei-devices/
1. make an account.
2. input necessary information to obtain "unlock password".
3. check

   >fastboot devices
   ******* fastboot 
   

4. unlock

   >fastboot oem unlock "unlock password".
   

   "phone unlock"ed
5. TWRP
Use TWRP for Huawei Honor 5X. It can be used in case of KII-L22, which is my phone model.

Tiny things matter:
I spent four hours with this...
#check your device is recognized.
>adb devices 

>adb reboot bootloader
#bootloader mode: white screen + (green)android dude.
#check "PHONE unlocked" AND "FRP unlock". (in red character on the screen.)

#flasshing the img.
>fastboot flash recovery twrp.img

#reboot.
>fastboot reboot

#reboot with recovery!!!
>adb reboot recovery

The last command. Do not be confused with "fastboot reboot".
some page instruct to run this command.
even try until it is succeeded. NOOOO! you will waste your time.
use the command above. 
It will work at the first time and always.

6. supersu install.

from twrp boot: install UPDATE-SuperSU-v2.76-20160630161323.zip.
reboot.

7. rename file! to silent the shutter sound.

from windows powershell.
> adb shell
# works only after supersu is installed.
> su  
# see your phone. supersu asks you to enable su on your phone.
> mount -o remount rw /system
> cd /system/media/audio/ui/
> mv camera_click.ogg camera_click.ogg.backup
and reboot.
The shutter sounds disappear!!
and you are a root on your phone.

8. from 2nd times
1. if su is missing somehow.

   from windows powershell
   > adb shell
   > su  # works only after supersu is installed.
   su: command not found. then,
   > exit.
   #reboot with recovery!! will do.
   >adb reboot recovery
   

2. Re-install supersu again(see above). Then delete videoStart.org etc, after su.
9. Reference
• Delete Shutter sound: http://android.stackexchange.com/questions/89/how-do-i-disable-the-click-sound-on-the-camera-app
• How to unlock bootloader on Huawei Device: http://www.stechguide.com/unlock-bootloader-of-huawei-devices/
• huawei gr5 Q2-K22 experience: http://forum.xda-developers.com/honor-5x/help/huawei-gr5-root-t3339948
• movie: https://www.youtube.com/watch?v=_iqwbLS9UFs