I suspect it is system-c, but I'm not a programmer, nor do I have any experience programming, so I'm not sure how I would conclusively tell.
Also, no , I didn't use the program you linked to, I just used Notepad++. The program you linked to does seem potentially suitable.
Anyway, I've made a decision. Yesterday, while awaiting a response from anyone on this thread, I decided to investigate translating the script of another game I have which uses RealLive engine and was released in 2017. I read a guide for RLDev and spent 3 hours to get it running, but when I finally ran cygwin an error was produced suggesting the RealLive engine for the game I was targeting wasn't supported and the seen.txt wasn't decrypted. Following this, I looked into the possibility that someone released newer tools to decrypt newer RealLive releases or decrypted the seen.txt of the particular game I wanted to translate, but unfortunately it seems that no one has.
I was disheartened by this revelation and as such, I've decided to abandon my attempts at visual novel permanent translation for the time being until sufficient tools are released for all the games I want to translate or I obtain the programming wherewithal to hack into scripts myself. My reason for complete abandonment of all projects as opposed to just the RealLive one is I was planning on paying for an unlimited character machine translation service, such as DeepL Pro, for a month and then just batch translating everything within that timeframe to save costs.
I've now decided on two courses of action:
1. Learn Japanese to read everything I want
2. Use a program called Textractor and use an API key from google cloud service (first 500,000 characters translated per month are free) or the CAT tool API key from DeepL Pro (30 day free trial, unlimited characters) to bypass the rate limit on translated text (VNR doesn't seem to support API keys).
I tried google cloud service translate and it works like a charm.
Thank you for your responses nonetheless @Infernoplex