There were previous attempts - by the Russians, I think - but they failed. I hope the Japanese succeed.
Probably also Japan, sometime ago. Using a deep sea submarine, something like that. Perhaps Japan always wants to explore various sources of resources.
The problem with such deep drilling isn't just that the rock at such depths is semi-molten, it's also the enormous pressure. They drill a hole and then the pressure crushes the hole and the drill.
This kinda falls under that whole "Just because a thing can be done doesn't mean it should be" saying.
I doubt it will ever occur in our lifetimes, if ever. https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole