Aizen and co. are in the dangai. And there's the Guardian. (Koutotsu - the Train thing inside the Dangai)
The reiatsu around it's gone, so logically, ... so they should hurry, says Gin
However, Aizen breaks the Koutotsu into tiny pieces. After some more lines - "Would you come? To the edge of reason, which is why we are headed to SS," says Aizen.
Ichigo and co. Ichigo says "eh?" to Isshin's words and gets headbutted by Isshin.
"It's no use talking about it all over again", answers Ichigo. "Don't you understand?!", says Isshin, "that monstrous reiatsu means we can't win for sure." says Ichigo.
"With those words, that means you understand his reiatsu... and the deep meaning to those words."
"Let's go." Even though Ichigo doesn't answer back. "If you're not coming, then you're not protecting anyone if you're just gonna sit there and cry." he says.
"Think about what Aizen being in SS means, if you're not going, then everyone in Karakura will be butchered by Aizen." Ichigo remembers Tatsuki and co. With that thought his feelings change and he asks Isshin to open a senkaimon.
Aizen arrives at SS. Karakura's situated a bit farther off, in a separate location. "Well, it ain't my fault but theirs, " says Gin.
Ichigo and company progress through the dangai. Isshin notices that the Koutotsu is missing.
"The Koutotsu is gone, that it's not here now is pretty convenient."
Just like the dangai's name, from the real word to SS, it's a place where time and space ceases to exist.
That's why the Koutotsu is here, so that anything that enters here doesn't exist for long.
Since it's not here now means I can teach you, says Isshin.
Ichigo asks what it is.
The final Getsuga Tenshou", say Isshin.
Karakura town in SS. Keigo opens his eyes. And then Aizen enters Karakura. To be continued.