His root tools uses two exploit - one is master key exploit (bug 9950697), another one is CVE-2013-6282.
No internet connection is required.
Xperia Z C6603/C6602 10.3.1.A.2.67 / 10.3.1.A.2.74 / 10.3.1.A.0.244
(Other confirmed devices: Thread in Cross-Device Development)
Z 10.4.B.0.569 couldn't be rooted with both exploit, so these root tools cannot be used with newer devices/firmwares than Z1 .257.
--- bug 9950697 ---
You can download root tool from Japanese website,
find "rootkitZ_20131112.zip" and download.
--- CVE-2013-6282 ---
You can download from this tweet.
*** Setup adb and enable USB debugging and Unknown Sources ***
Extract zip and run install.bat and follow the instructions.
If your device reboot and cmd says "完了しました" or "--- all finished ---", rooting is done.
If this roo tool helps you, please consider donating to him via Paypal.