Theresa May's call for early election caused institutions to revise their targets for the pound, and a sharp increase to 1.29 on GBPUSD.
As JPY has been bought aggressively for days, I believe this is about the time for a short covering.
Combine these 2 ideas with a technical signal that GBPJPY is breaking previous highs, I'm targeting 142.00 as the next stop.