I am so lost. I'm trying to remember an old anime show and it's killing me.?

I remember that when I was in maybe third grade which was about six years ago, there was an anime show on cartoon network involving this brother and sister that would log onto this virtual world. I don't remember much of it but I do remember the sister getting abducted by something and that she was being held captive in the stomach of the thing and the brother had to save her but he couldn't find a way that didn't involve killing her. I also remember that at the end of the show when they played the credits they would go through a ton of pictures and one of them was of a photo frame with flowers next to it and then I remember there being a scene of metal bars in which the girl was held captive for a while, I think. It's been killing me to find out what the show is because I never saw how it ended and I've been searching for it for years because it was ended. I remember in the last episode I saw the brother was hiding behind columns, a few yards away from the giant pink gelatinous thing that had the girl in it's stomach but there was this figure watching the boy from afar and the boy ran after the figure, I think (my memory is a little foggy) and that's all I remember....