A rough summary for X11, less the side story at the end, compiled partly
from my friend Nataku's summaries.

Kamui is having flashback of what happened since he returned to Tokyo.  
(Take that as a summary of X1-10 in less than 20 pages)  He then gets
dressed and heads down the stairs to breakfast.  Kamui, Yuzuriha, Sorata,
and Arashi are living in a house together and going to CLAMP school.  
Everyone worries over Kamui. They sit down for breakfast and then go to
school.  Sorata for some reason isn't wearing uniform.

Yuzuriha takes off to middle school.  Kamui leaves Arashi and Sorata to
where Kotori's buried.  Kamui gets to his classroom and immediately called
out by Keiichi Segawa, an energetic classmate.  He seems to like Kamui
very much and is very cheerful. He asks Kamui if they can eat lunch
together.

During lunch, Kamui rushes off to another part of campus and meets up with
Subaru for tutoring.  Kamui wonders why Subaru quitted school -- because
of Sakurazukamori?  Subaru starts tutoring Kamui and lights a cigarette.  
Kamui comments on it and Subaru tells him that contrary to most people,
cigarette has the opposite of adverse effect on him.  He said brand
doesn't matter, and Kamui wonders if that is also because of
Sakurazukamori.

Hinoto wakes and comments on not having any different dreams of the
future.  Daisuke, Souhi, and Hien were concerned about Hinoto.  Daisuke
comments that it must be harsh for Hinoto. Hinoto thanks Daisuke as he
leaves, and again in her thoughts, then says "But I...."

Keiichi finally finds Kamui for lunch but apologizes as he notices that he
broke in on a tutoring.  Subaru tells Kamui to go have lunch.  Keiichi and
Kamui leaves.  Suddenly, an earthquake comes and Kamui stands up in
surprise.  Keiichi pushes him to the ground and shelters him with himself
until the quake stops, then yells at Kamui that he shouldn't be standing
during an earthquake.  He them says that it's unusual that the Campus is
rocked by an earthquake.  Kamui associates it with Dragon of Earth.

Later, all the DoH less Subaru are gathering in a fast-food restaurant
discussing the earthquake.  Sorata asks Kamui what he thinks of the quake
and Kamui says it feels different.  Sorata agrees.  Kamui says he can feel
the Holy Sword.

The place where the quake was centered in Ikebukuro where Sunshine 60 is.  
It created some damage to Nataku's lab.  Later, they find out nataku's
data has been downloaded by someone else (the beast).

Fuuma is sitting in Kanoe's chair.  Nataku walks by and Fuuma tells it
they've gotten its data.  Nataku comments on not wanting to go back but to
stay by Fuuma's side.  Fuuma asks why.  Nataku replies that it doesn't
know, but that it doesn't want to be separated from Fuuma.  Nataku tells
Fuuma that he resembles its father.  Fuuma asks what its father called
Nataku.  Nataku told him, 'Kazuki.' Fuuma then calls Nataku "Kazuki."  He
strokes its hair and says that if that is Nataku's wish, he will grant it.

The DoE and Kanoe discuss how different (gentle) Fuuma is now and that
Kanoe has a bad feeling about this.

Satsuki finishes the download of Nataku's data and touches a picture of
Yuuto.  Kusanagi is in a park, surrounded by cats.  He talks to them and
they reminds him of the girl with the same name (Yuzuriha Nekoi -- neko
means cat).  Meanwhile Seishirou is lurking on top of tall buildings.

Another day of school.  Today is Kamui and Yuzuriha's turn to make
breakfast.  Kamui says that he's not going to be home for dinner that
night because he'll be over at a classmate's house.

That evening, Kamui and Keiichi arrive at the Keiichi's house, which is
close to the Sunshine 60.  Keiichi's mother makes dinner for the boys and
the takes a tray to another room.  Keiichi says it's for his father who
died from the earlier earthquake (i.e. the one caused by Seishirou).  
After dinner, Keiichi walk Kamui back home.  On the way, another quake
strikes.  Kamui struggles out of Keiichi's body-shielding and tells him
not to worry about him and go home.

Earthquake hits Sunshine 60 as Nataku about to kill the scientist and the
president.  The president asks Nataku's intention, Nataku replies this is
what Fuuma wants.  The Prez calls him "Kazuki" as Nataku was about to give
the final blow.  Fuuma senses Kamui and says that he's coming and takes
off.

Sunshine 60 is falling.  Kamui realizes that if it falls-- "--everyone
will die," Fuuma finishes the thought for him.  Kamui turns around and
stares at his former best friend.

Nataku arrives and throws the unconscious president between the two Kamui.  
Fuuma starts to hurt the prez.  Kamui throws himself between Fuuma and the
old man.  Fuuma starts to play with Kamui as Kamui takes the president
with him and gets out of the way.  Fuuma damages the building more.  As it
tilts, Fuuma asks Kamui why he doesn't make a Kekkai, and then says that
it's impossible for Kamui to do it.  Kamui seems to want to know why, and
Fuuma replies that since he's the other Kamui, he knows everything about
him.

As he lifts Kamui up by the throat trying to finish him, Subaru appears
with his spells and 'falcons'.  Nataku helps with dodging the flying
papers.  Fuuma turns and smiles at Subaru, saying that he has come to help
Kamui.  Subaru freezes, as Seishirou's image seems to appear behind Fuuma.  
They look alike, he thinks.  He clears his thought and the last scene, we
see Subaru creating a star-shaped kekkai.

X11 side story is Subaru's.