I don't have the TY2 mermaid myself, but it sounds like it uses an 'encoded' OBJ.

RTE Encoder should allow you to extract the new OBJ: http://www.rtencoder.com/

There's a handy illustrated tutorial on the process: http://www.rtencoder.com/2007/09/21/rtencoder-decoding-tutorial/

The key file to decode the RTE is probably the original OBJ for TY2