Could Japan make Britain look like the aggressor?

Could Japan provoke a British boarding response and then portray Britain as the imperial aggressor?

Probably not: the merchant ship was already in Royal Navy custody, so a Japanese attempt to board it would still appear to violate protected British space and would be framed as Japanese aggression.

The British sailors could continue stating that they were following orders and refer any dispute to the senior officer aboard HMS Birmingham. By that stage the merchant vessel was being treated as under Royal Navy protection and, in the discussion's diplomatic framing, as British sovereign space. A Japanese boarding party would therefore have to initiate the physical intrusion rather than merely respond to a British attack. The effort to reverse the propaganda burden would likely fail because the visible sequence still began with Japan trying to retake a protected British-flagged ship.