Verdict: You can build, fight, and upgrade perfectly. You will miss the entire narrative and might get lost during specific "gather item" fetch quests without external help.
Before you begin, it is important to manage expectations regarding the availability of a patch. danball senki w psp rom english patch work
Note on Files: Be extremely careful when downloading "English Patched ROMs" from random sites. These often contain malware. It is always safer to apply a patch to your own backup file (.xdelta or .ips patches) rather than downloading a pre-patched ISO. Verdict: You can build, fight, and upgrade perfectly
The latest effort from the now-defunct Danball Senki Translation Project (circa 2017-2019) released a patch labeled v1.1. This is the "working" patch that most users refer to. Note on Files: Be extremely careful when downloading