Now my understanding of Japanese markets is scant at the moment (I'm planning on leanring more about them next year) but some of the scenarios you say occur here as well in Australia. Our stocks do gap up or down significantly off the tails of US action however I've managed to notice that underlying markets drive the individual stocks so I watch those closely.
The best example I can give is the mining sector. Our biggest stocks are all miners like BHP Billiton, Rio Tinto, Newcrest, Paladin etc... This is where a bit of fundamental analysis comes into it. I like to find out a bit about the stock and what mining sector they specifically operate in i.e: are they gold miners, uranium miners, nickel, iron, zinc etc...
I like to keep an eye on the underlying price of their main resource as the stocks do track these markets quite closely. Uranium prices over the past 8 or so weeks have dropped off from $135 US/pound to $90 US/pound of U308.
The drop in Uranium prices has effected my uranium mining stocks. Even though over the last week the domestic SPI has recovered from the fall, the downward trend of uranium prices on world markets has been pulling back on general Uranium stock price recovery.
That being said, the same situation may occur in Japan. Granted in Japan there are not so many mining industries as here in Australia but the principle still applies. I think that you can get better clues to market movements in your domestic equities markets by doing a bit of research on the individual stock and then its key stake holder and subsidiary markets. This can help you gague the strength of a move against a highly correlated market and is free from the bias of Tape or L2.
If you use somehting similar in combination with a simple MA crossover you might be able to start spotting some incresingly obvious combinations which can help generate both short and long term long/short signals.
Hope that helped
