GBP/JPY has finished the upwave from 135.11 to 130.63. According to wave count on larger timeframes that was subwave A (colored magenta in the chart) within long term impulse wave C - colored plum in the chart. Now the price stands at the beginning of potential corrective subwave B. The targets of the corrective upmove are Fibonacci retracements of 135.11-130.63.
Resistances:
- 132.34 = .382 retracement
- 132.87 = .50 ret
- 133.40 = .618 ret
If the downtrend resumes the immediate supports will be Fibonacci retracements of 122.49-139.93, and expansions off 139.93-130.26-135.11, 135.11-130.63-132.27.
Supports:
- 129.50 = contracted objective point (COP)
- 129.15-13 = confluence area of .618 retracement and COP
- 127.79 = objective point (OP)

Overbought/Oversold
Assuming that the medium term trend is down it's preferable to try shorts when the Detrended Oscillator gets above the zero level (current prices) or into the overbought area (10-25 pips above the current prices).
Read more on how to apply Fibonacci studies to calculate price targets.