So not a big surprise this game uses 椎名里緒v2.5, my best advice is you see *.war (and RIO.ini), just give up the idea to extract the game, unless you are welling to spend time to study how those resources extractors work. For some reason, all those tools are open source on GitHub.
Here is the 3 extractors' result:
1. arc_conv (ver. whatever 54, there seems no update on .exe itself after this version): warcscan produces a key [250-470A4722472F472C848E8C87844FB24C45], but with the key arc_conv still could not parse *.S25 from PARAAKIBA_G1.WAR or PARAAKIBA_E1.WAR. The key seems working as PARAAKIBA_D.WAR can be extracted with some readable *tga. BTW: all *.S25 and unsuccessful files extracted by this tool has only a file name and 0kb.
2. crass: (no way to ask it to use the key from arc_conv) auto unpacked everything, get all garbage *.S25 with reasonable file size, you might try something to decode those *.S25, e.g.: 3c1u/S25Viewer, morkt/GARbro/blob/master/ArcFormats/ShiinaRio/ArcS25.cs, or if someone made a Susie32 plugin
3. GARbro (ver.1.5.44): as the GUI suggests, you can only pick decoder of ShiinaRio ~2.34 or ShiinaRio 2.36~2.38, so
I say all of these tools support up to 椎名里緒v2.38, it's more of a parsing problem of resources rather than image decoder of *.S25. (considering you probably need to manually marge images from parts, sometime it's just better to wait someone post a CG pack anyway, and for character's stands most of these modern system uses emotion so you won't be able to view the picture or anime with standard viewer, even the resources are correctly extracted)