GBP/JPY is moving within wave C of long term downtrend - colored light green in the chart. And within this wave there are A and B subwaves (colored royal blue), with subwave B still developing. The targets of the upmove are Fibonacci retracements of 132.30-128.19 and expansions off 128.19-129.53-128.62, 128.62-129.3-129.39.
Resistances:
- 129.96 = objective point (OP)
- 130.20-25 = confluence area of contracted objective point (COP) and .50 retracement
- 130.70-73-79 = confluence area of OP, .618 ret and expanded objective point (XOP)
- 131.51 = XOP
If the price reverses to the downside the immediate supports will be Fibonacci retracements of 128.19-129.93.
Supports:
- 129.27 = .382 ret
- 129.06 = .50 ret
- 128.85 = .618 ret

Overbought/Oversold
Assuming that the medium term trend is down it's preferable to try short positions when the Detrended Oscillator gets above the zero level (current prices) or into the overbought area (20-30 pips above the current prices).
Read more on how to apply Fibonacci studies to calculate price targets.