I took a look at this, the texts are actually inside [root]/ETC/SCENA.DAT, but each byte of text is XOR'd against 0xA5, the actual format of the file is fairly simple:
//int = 4 bytes
int line_amount //Amount of lines in the file
int text_size //Size of the text section file_size - 8 - (line_amount * 4)
int line_lenghts[line_amount] //some lengths are -1 (0xFFFFFFFF), these get ignored
And after that the actual text (XOR with 0xA5 to get the real text), each line delimited by their length
Can this be converted with a quickbms script? Atached is the actual SCENA.DAT, for testing.
Also, kinda related, rebuilding the whole data_ys1.na archive with ysext.exe makes the game unable to boot, had to use -a can this be fixed?