Eh the Japanese pretty much imported the BGB wholesale, a metric fuckton of countries have civil and criminal codes that root in either the French or German traditions. Their system is also generally firmly rooted in civil law, that is, precedent is non-binding.
This is mostly a case of politicians not wanting to stir controversy, I think: While most Japanese would be in favour it’s a change and on top of that a change that would really piss off a minority so in the interest of conflict averseness the can is getting kicked down the road.