I wouldn't try to break it off either. Too much risk of messing up the case.
Penetrating oil around the flange. Apply heat to the case but not the plug. Heat it until the oil starts to smoke, then stop and let it cool. Do that 3-4 times before you try to turn it. The heat cycles will help the oil get in there and break the joint loose.
Grip it with vice grips and tap the vice grips with a hammer. A manual impact driver might also work. Or, cut a slot in it, stick a cold chisel in the slot, put a wrench on the chisel, and tap the wrench with a hammer.
New plug... https://www.ronayers.com/oemparts/a/yam/50043509f8700209bc78bc6d/oil-pump
Put a bit of oil on the threads of the new plug.
This shall pass, be still and know.
2006 XT225, UNI filter, ProTaper bars, MSR handguards, SS front brake line, Shinko 241's.