How bad is it? Unusual kaiju with some very poor bits.
Should you see it? Sure! I liked it.
Japanese monster movies made by the smaller companies that didn't specialize in it tend to be weird; this one is gorier, but with much less action (the giant bird doesn't even appear until near the end). The dubbing is poor and the soundtrack is amazingly irrelevant - it actually distracts you from what's happening. Investigating the wilderness near Mt. Fuji, a woman falls into a hole and breaks a stone egg. Then cattle and horses start losing their heads. Soon there are reports of a sea monster and then it's the standard people vs. monsters stuff, except that this one rips off entire scenes of "Jaws."