Japan told the World Trade Organization (WTO) it will take steps to retaliate against the US. Initially they said they would abide with the tariffs on steel and aluminum.
They are considering tariffs on US goods worth $451 million, an amount equal to the US placed tariffs. They failed to set a firm date on when they planned to impose the tariffs. This might be seen as a ploy to start negotiations to get the tariffs to Japan repealed or reduced. The US has granted some allies a delay but Japan was not one of them.
Up till now, Abe and Trump seem to have a close relationship especially in respects to North Korea. Now that North Korea has begun to supposedly dismantle their nuclear test site, the relationship is becoming frayed.