I have tried some of the methods such as booting the phone into Recovery Mode. I was told to power off the phone, start it, then when pink LED lights up I have to quickly press Volume Up multiple times until the screen shows the Android logo (which is the green robot). The situation my phone in isn't quite like the expected; since it's in bootloop state, I have to force restart it (by holding Power button + Volume up and wait for a vibration), quickly pressed volume up several times. However, the LED only lights up blue color (not flashing), the screen stays black and nothing seems to be happening until a force restart is initiated.
Right now I don't think flashing ROMs or restore phone to factory setting are the solutions for me because I only started using this Xperia Z recently and didn't make a backup (who knew it'd be so fast that I literally killed it).
By the way, is there a possible way to access files during the blue LED part?