[GoNative]

As far as I can tell the political issues between the two countries have had little effect on the economic relations between China and Japan. They have the 3rd largest trading relationship in the world. Political relations should improve but both countries have a lot of mostly historical issues with the other and these will take time to mend, especially with both being very proud nations making compomise difficult to reach at times.
If Japan really wants to improve relations with SEA it really needs to accept responisbility, apologise and possibly make some reparations for the damage it caused during WWII. It's arrogant dismisal of such issues in the past hasn't helped it one bit.

The real question here is what benefits would Japan receive by distancing itself from the US? How would it help Japan? The US is still Japans biggest trading partner and throughout it's history I believe it's had a significant trade surplus with the US. Some political distancing may not be a bad thing but not at the cost of trade relations.