The Japanese article is here. The english version is in the Japan times here. This might be evidence of using Kansai airport more proactively as it is outside of populated areas and so can operate 24 hours. But I think the charges would have to come down, and its not a final destination so links to Kanto would have to be 24 hours too. Probably also need to listen more to LCC (Low Cost Carriers) before it could become a reality.