Direct answer
USD/JPY is likely up because traders are assigning a higher probability to a constructive outcome across its main catalysts. That does not automatically mean the move is healthy. The right read is whether strength is broad, clean, and durable.
Most likely bullish catalysts
US yields
Improving us yields can support a stronger bid in USD/JPY.
Bank of Japan policy
Improving bank of japan policy can support a stronger bid in USD/JPY.
carry trade demand
Improving carry trade demand can support a stronger bid in USD/JPY.
dollar strength
Improving dollar strength can support a stronger bid in USD/JPY.
What confirms the rally
- Confirm the move is supported by us yields rather than a thin short squeeze.
- Check whether leadership across related forex markets is also improving.
- Only trust continuation if the chart holds gains after the first impulsive push.