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.
Resistances:
- 130.25 = .50 retracement
- 130.73 = .618 ret
If the price reverses to the downside the immediate supports will be Fibonacci retracements of 128.19-130.06 and expansions off 130.06-129.08-129.94, 135.11-129.74-132.30, 132.30-128.19-130.06.
Supports:
- 128.96-90 = confluence area of objective point (OP) and .618 ret
- 128.35 = expanded objective point (XOP)
- 127.52 = contracted objective point (COP)
- 127.37 = super expanded objective point (SXOP)

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 (10-15 pips above the current prices) or into the overbought area (35-45 pips above the current prices).
Read more on how to apply Fibonacci studies to calculate price targets.