Technicals: GBPJPY has been trading far above any pivot on the weekly chart. On 1D, we formed double top earlier this year (yellow highlight) with its second peak giving a birth to the symmetrical triangle. We are near the point where such triangle usually leads to a breakout. I don't there is any technical indication for the direction of the breakout, although the recent lows on 4h were agressively bought (picture follows).
Fundamentals: Both currencies are considered bearish to the overall market. GB's economy isn't doing great with the inflation running high and Japan keeps the rates way too low.
Catalysts: → Bankers are attending Jackson Hole Symposium. Anything they say to public may propel either currency in either direction. → Japanese CPI will be announced by Friday. Anything above expectations may spring speculations about shift in Japanese rates policies.
I would rather be shorting this pair as there is far more room.