GBP/JPY is developing wave C of medium term uptrend - colored magenta in the chart. This wave in its turn has 5 subwaves (colored red) and wave A of potential corrective A-B-C cycle that is going against the 5 waves. The targets of the downmove are Fibonacci retracements of 135.10-139.60, 130.18-139.60 and expansions off 139.60-138.03-139.54.
Supports:
- 137.97-88 = confluence area of objective point (OP) and .382 retracement
- 137.35 = .50 ret
- 137.00 = expanded objective point (XOP)
- 136.82 = .618 ret
- 136.00 = .382 ret
- etc.
If the uptrend resumes the immediate resistances will be Fibonacci expansions off 122.49-133.04-130.18, 130.18-133.76-132.38, 132.38-136.03-135.10.
Resistances:
- 140.73 = objective point (OP)
- 141.01 = expanded objective point (XOP)
- 141.75 = super expanded objective point (SXOP)

Overbought/Oversold
Assuming that the medium term is now up it's preferable to look for longs when the Detrended Oscillator gets below the zero level (current prices) or into the oversold area (current prices), or hits Fib support area at 130.97-88.
Read more on how to apply Fibonacci studies to calculate price targets.