Microsoft has removed a media creation tool for Windows 8 and left only the one for Windows 8.1. You can still use it to repair the corrupted boot files on your Asus laptop. Here are the instructions:
First, go to this webpage:
It describes how to create a Windows 8.1 installation media. Click on the Create Media button and run the downloaded tool. Select the language, edition and architecture. Make sure to match the one that is installed on your Asus laptop.
Click Next. You can choose between creating a bootable USB flash drive or a bootable disk (ISO file). Since your Asus laptop doesn't come with a CD/DVD, select the USB flash drive option and click Next. Note that the process will format the USB flash drive, so make sure to transfer the important files to your computer first.
It could take some time for the Windows 8.1 files download from the Internet.
Once done, plug the USB flash drive to your Asus laptop and start it. If nothing happens, you need to access the BIOS and set booting from the USB device. Pressing the F2 key while your Asus laptop is powering on should take you there. Go to the Boot tab and set USB device or similar name at the top of the boot priority. Press the F10 key to save the changes and exit the BIOS.
Your Asus laptop should then restart and load the Windows 8.1 from the bootable USB flash drive.. You will then see the Windows Setup window with two options:
1. Install Now
2. Repair your computer
Click on "Repair your computer". The "Choose an option" screen will appear. On that screen, click on "Troubleshoot", and then click on "Advanced options". First, select "Automatic Repair" which should automatically detect and fix all found boot problems. The computer will restart. Let it boot to Windows 8 as usual. In case the problem remained, boot from the USB flash drive again, and follow the same steps, but this time select "System Restore" instead.
On the System Restore window, select a date you know your Asus laptop worked just fine. The process will attempt to restore all Windows and program settings to that date, so hopefully, this will solve the problem.
Let me know how it went.