Laportea cuspidata

A member of the Urticaceae, ie the nettle family, from Myanmar, China, Korea and Japan, where we saw it growing in mountain forests. Possessing a sting like a tiny electric shock (and lasting no longer), rather than a nasty lasting burn, this makes a perennial to about 1m tall, with attractive well toothed and deeply veined foliage, covered on the upper side with tiny black conical non-stinging spines. White flowers top the stems in late summer. Almost definitely edible and highly nutritious, but that needs confirming.