Wasn't this mostly previously answered, and it seemed Aizen wasn't completely surprised then anyway?...
It was explained that it blocks reiatsu, but not that it makes you invisible... This might as well mean that Tessei has x-vision or heat-vision in his eyes, since he was able to see Urahara :O. This explain why he always wore sunglasses .
Originally Posted by Xerenix
That's because HIS bankai takes a great toll on his body and with a wound that deep, it will most likely kill him or put him near death.
I really liked how Isshin used his blood to attack and makes me wonder if all his attacks is like that if the bankai takes such a toll on his body.
Hmmm, like let's say, about 1 liter of blood coming out of his body and forming a fire beast (phoenix ?) ? A few drops allowed for his attack to expand this much, so it might be quite something.
A real Colossal Sword, is only Colossal when it is at least 5 times bigger than the thing you pilot: