When looking for a "highly compressed" ISO of for the PS2, it's important to understand that while compression can reduce file size for storage, the game must be decompressed to its original size to run on an emulator or original hardware. The original game is quite large as it spans two DVDs. Optimized Ways to Play
Optimizing Your Yakuza 2 Experience: PS2 ISO Compression Guide
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is the best way to keep Kiryu's second adventure on your drive without sacrificing performance. Why You Need a Compressed ISO