I knew practically from the very beginning that Sai would disappear. But I expected it to be like the last chapter, a kind of bittersweet finale. But he left kind of early, and he just disappeared without a word. Then, when the series ended without him showing up again, it was just so so sad, lol. What's worse, because I saw that I had more manga to go (the side stories), I didn't know I had finished until after I started the first side story! I couldn't help but cry, lol.
However, there was one panel when Hikaru was playing a game in the Hokuto cup, against the Chinese player, I think. The first one, before he played Korea. And they showed him leaning over the go board to place a stone, and above him, was an even bigger version of himself, doing the same thing. This rather than Sai. I loved that. He had to become the player he was going to be. He was trained by Sai, of course, but in the end he was going to go further. It was a great way to show that.