If someone says,
"I'm visiting Tokyo now,"
does it mean they are already in Tokyo?
It certainly implies that the person is visiting Tokyo at present.
But the sentence could also be used in other contexts, for example:
If the person was merely passing through the airport;
If the person was visiting Tokyo next.
Or
If the person was playing a computer game involving various cities.
Tokyo might even be somebody's name.
Now is a notoriously fickle word. I'll do it now or just now is a commitment frequently honoured in the breach.
In short, you can't be certain that the statement is meant literally.