This is the most common error. It means your Japanese ROM is not the correct revision. Ensure you have the original, untrimmed release of Medarot DS . Some "pre-patched" ROMs circulating online are corrupted. Use a verified No-Intro ROM set.
If you find a patch file (usually in .ips , .ups , or .xdelta format), follow these steps to play: medarot ds rom english patch
Be cautious of fake “v2.0” patches on random ROM sites – only v1.0 from the original team is confirmed complete. Report: Medarot DS (Medarot DS) English Translation Patch