Hi tatsudojo! Before I tell you how to use Unity Studio (which I recommend getting the newest version called Asset Studio
here), I can save you some time by saying this: the APK doesn't seem to contain anything you're looking for (sounds, lines, and whatnot), so you don't have to worry about going through it in Unity Studio/Asset Studio. Instead, you can focus on the downloaded game data.
So, getting started, open up Unity Studio/Asset Studio and navigate to the top left corner of the window. From there, select
File, then
Load Folder. Navigate to wherever you have the game data stored on your computer, and select the main folder that all of it is located (I selected the
com.netmarble.kof folder). Then, wait a bit while Unity Studio/Asset Studio does its thing, it could take a while to load everything in (wait for the little green progress bar down at the bottom of the window to finish). When everything is loaded, navigate to the
Asset List tab and you'll see a list of everything that Unity Studio/Asset Studio found. Now, to keep you from scrolling for hours to find every audio clip, I recommend you click on the
Type category above the list, allowing you to sort by asset type. Then, scroll down to where the
AudioClip type starts appearing, and look through the files. When you find you want to extract (or a whole bunch by single clicking on one and then [Shift] clicking another down the list to select a whole bunch of them), simply right click on it and click
Export selected assets. Choose a place to export them to, and voilà, you've got your sound effects!
Included below are just a couple sound files to prove it works!
Namaiki_Skill_01_Voice_01.wav
Namaiki_Skill_01_Voice_02.wav
Namaiki_Skill_02_Sound_01.wav
Hope this helps, cheers!