EUR/JPY tells you how many Japanese yen one euro is worth. It is a "cross" — neither side is the US dollar — and it is one of the most widely traded crosses in the world. Because it blends the euro with the yen, it behaves as much like a mood gauge as a currency pair.
The first driver is the policy gap between the European Central Bank and the Bank of Japan. When the ECB holds rates above the BoJ's, the euro tends to attract buyers and EUR/JPY drifts higher; when that gap narrows — the ECB easing, or the BoJ tightening — the pair can fall. As with other pairs, markets usually move ahead of the decisions, on expectations for growth, inflation and policy in both regions.
The second — and often the louder — driver is risk sentiment. EUR/JPY is treated as a classic risk-on/risk-off barometer. The euro is the more risk-sensitive side, while the yen is a safe haven, so when global confidence is high the pair tends to rise, and when fear takes over money rushes into the yen and EUR/JPY falls. Traders often watch it alongside European equities for confirmation of the mood.
It is most active during the European session and the London–New York overlap, with the Tokyo session moving the yen leg overnight. Because it reacts to both European fundamentals and the global risk tone at once, EUR/JPY can trend strongly — which is exactly the kind of balance Robin weighs into a single read, complete with an entry, a stop and a target.