Ico: I'll always be alone

I cleared the watertower a few days ago, and saved just after entering the West Tower.  Given the difficulty I had with the East Tower - well, less the difficulty, more the length of time it took to get through it - I was expecting the West Tower to take an absolute age to complete.  In fact, it was pretty simple and disappointingly similar to the East Tower (though the route through was significantly shorter).

After opening the main gate, massive plot things occurred.  I am guessing that I won't be able to save the game after this point, so I'll have to complete it in one go.