KeiyuuS

For a few days now I've tried my hand at editing CGs for a couple VNs, and for the most part it's been going pretty well. A lot of tools out there that help with extracting and repacking things into kirikiri and realive. Now though, I wanted to try my hand at another VN I've been enjoying lately, Shukusei no Girlfriend. Problem is, unlike Kirikiri and ReaLive, I'm having a significantly harder time finding tools to extract (and repack) the CGs. I tried using Crass, Arc_unpacker, Whale-tools, and I've even looked into asmodeon's whale extractor as well, but no dice. Just get errors. Does anyone know of any tools that would work on it? Am I just doing something wrong with the tools? Should I bite the bullet and learn how to reverse engineer on the game's engine? Any replies would be greatly appreciated.