[shmaster]

Originally Posted by BPD Renegade

Spoiler for what happens to celty's head:

Just to be sure I warned you, this is what happens up to the end of the entire series!

Spoiler for warning:

Celty is indeed reunited with her head, but she eventually goes berserk. Eventually, Shinra is able to break through and it's severed once again (I think Shinra used Saika to do it, but I'm not certain at the moment). At the end of the series, Celty's headless body remains with Shinra, and her head gets taken to the States.

A little more elaboration

Spoiler:

After getting her head back Celty also got her memory back. With that, she decided to leave Japan back to where she came from. Of course Shinra won't allow that. He catches up with Celty by letting himself gets contaminated by Saika and threatens Celty to come back or else he is going to take his own life.
Celty of course turns back to stop Shinra, and Shinra use that opportunity to sever the tie between Celty's body and her head using Saika.
Afterward, Celty's head got taken to the US, while the body still stays with Shinra. But this time Celty had all her memory in tact, as she lost her head this time while she is still conscious, so losing her head did no damage to her memory.
Shinra was grateful after finding that out, as Celty decided to stay with him by her own account.
This is a pretty important transformation of Celty's character as she finally accepted her identity as a monster who lives in a human society. This also lead to an important action she did in SH arc.