Compression ask (Also about romhacking)

[apraxiumRum]

Hi! Right now I am researching the possibility of making text translation for Dragon Slayer 6: The Legend of Heroes II for the PC Engine CD. (So no promises!  Sorry!)
At first, my hopes gotten up when I discovered VirtualRip! Imagine how it felt when I found text in the datatrack for the game! In S-JIS none the less! All I have to do is just mess around and ask questions after questions, and maybe something good might happen.
Wait!? Where's the menu, the items & weapons, the spells, locations, NPC dialoge, enemies etc.    
So it turned out the text I found apparently reserved for the intermissions cutscenes that happen within chapters, (Such as Selios's Departure). And there is some instances about PASS and GOLD and such.
The things I could think of is that compression was involved (There's lots of gibberish in the datatrack). But instead of the usual 'FF' in replacing parts of messages like LSZZ, there is barely anything to make sense of.
I realize that I should learn the thing called compression, and try to use Mednafen's Debugger more often, But I am feeling pretty much lost.
Does anyone know where a beginner like me should look for clues? It just that I never understood how compression works to apply it here.

[cabbage]

I've never looked into LoH II so I don't have any specific advice.
But I did a quick google search for "falcom compression"--
https://www.romhacking.net/forum/index.php?topic=17666.msg256702#msg256702
https://heroesoflegend.org/forums/viewtopic.php?t=289
Maybe these will help? Good luck~

PS: what is "VirtualRip"?

[apraxiumRum]

Thanks for the pointers.
I currently trying an overview made by dshadoff, maybe it'll be what sets me in the right track.
By the way, my bad, I meant "TurboRip".