If the files are taken from Evil Twin - Cyprien's Chronicles, there is currently no way of playing them as they stand.
The .dcs files in this game are (standard?) Yamaha AICA ADPCM, you can convert them to GENH and play with VGMStream with these settings:
Input File Format: Yamaha AICA 4-bit ADPCM
Header Skip: 0
Channels: 2
Frequency: 44100
Interleave: 0x4000
No loops
Or if the file plays weird after that, try using these
Input File Format: Yamaha AICA 4-bit ADPCM
Header Skip: 0
Channels: 1
Frequency: 44100
Interleave: 0
No loops
Haven't tried all files yet, so there may be special cases requiring different Frequency/Interleave settings.
Hope this helps.