I love g/t stories where one of the characters has their true size hidden. There's something about that particular tension where only one party knows the truth, or even were neither know and its solely the audiences burden!
And so many different ways for it to take shape.
Perhaps the giant and tiny are separated by a wall or even screen in a world were both kinds know of but don't interact with each other. Unknowingly the two build a bond until they decide to meet up irl and get quite a shock!
Maybe a inventive tiny build themselves a robot to pilot so they could live in giant society as tinies aren't liked. The tiny makes friends but they are terrified of what will happen when the 'friends' find out. (an inevitability of course)
Or a cruel giant messes with the wrong person and is made to walk in much smaller shoes. If they ever want to be their natural size again they must learn to swallow their pride.
It's a trope that I really need to write more of...