The Final Battle is the 20th chapter of Tsubasa: Reservoir Chronicle.
Syaoran reaches the upper level of the palace, where the Ryanban's son is awaiting him. The son, with the help of his father's magic and the power of the feather, has been transformed into a muscular monster. He attacks Syaoran, who manages to evade him by a hairline.
Fai and Kurogane are reaching their limits in their own battle with the Kiishimu. Their clothes and skin have been burned by the water. Still, she continues to attack, the water globules increasing in size and speed. She comments that only one other person has been able to hold out as long as they have -- and that person was a female Shinban from Ryonfi. Fai surmises that that was Chu'nyan's mother. The Kiishimu says it could very well be the mother. She compliments them on having been able to last against her this long, but she is under the control of the Ryanban and the time has come for them to die.
In one desperate move, she calls forth a wave of water, unleashing it on Fai and Kurogane. Kurogane says that if they're caught in that water, they're dead. Unexpectedly, Fai replies that he "doesn't die that easily". Kurogane asks him if there's any way he could use magic to stop the wave heading straight for them. He himself can't die yet -- he needs to get back to Japan. Their only option is to leave this world immediately! Fai agrees, musing that he can't stay in this world too long either, as there's a man sleeping under water who would chase him once he awakens. The only way he can run is to go to as many worlds as he possibly can.
The wave reaches them. The Kiishimu believes that the battle has ended -- when suddenly, Fai swoops straight toward her! She reels back a little and asks why he is so eager to meet his end. Fai then backs away, leaving Kurogane to make the finishing move. But the Kiishimu stabs him in the chest with her razor-length nails!
Meanwhile, Syaoran's battle with the Ryanban's son continues. He is overwhelmed by his opponent's otherworldly strength, and has been pummelled several times. The son grabs Mokona with the intention to hurt it. Syaoran intercepts, kicking the creature out of harm's way. Syaoran aims hit foot against the Ryanban's son's face, getting ready to end the fight. The son grabs his injured leg and twists the wounded area. The son boasts that kicks are no match for his strength. A wounded leg cannot guard against him. Syaoran calmly replies that the raised leg isn't there as guard, as he counterattacks with a good strong kick from his other leg that sends the Ryanban's son flying.
The action shifts back to Kurogane, who escaped certain death... because of a magazine! He had hidden the issue of Shonen Mangayan he bought in Hanshin between his clothes, thereby protecting him from the Kiishimu's claws. He then attacks her, breaking the jewel on her forehead. Around them, the room returns to normal. He cautions her from using any more of her tricks -- when to his surprise, she kisses him on the cheek. Apparently, within that jewel was magic that kept her enslaved to the Ryanban. Had she been given a choice, she would not have chosen to battle for the Ryanban against Fai and Kurogane. She tells them that the Ryanban is at the highest level of the castle, and that Syaoran may have already reached him.
The Ryanban has been watching the progression of the battles through his crystal ball. He has seen both his son and the Kiishimu defeated. The crystal ball containing Sakura's feather is cracking...
Mokona and Syaoran reach the Ryanban's chambers. Mokona again feels the weird magic surging, but because it was tossed around by the son, feels a bit dizzy. Syaoran glances up -- only to see Sakura and Chu'nyan captured in a floating sphere by the enemy! The Ryanban strides toward him, an arrogant smirk on his face and Sakura's feather in his hand.
The Ryanban still believes that Syaoran is the amenosa, and is strangely proud that if he is able to defeat the boy, it'll mean that he can defeat the amenosa. Syaoran ignores him, and demands that he release Sakura and Chu'nyan. In a quick motion, he moves toward the Ryanban and kicks the crystal with the feather out of the enemy's hands. The feather shimmers, knocking the boy out of balance. The Ryanban boasts that should Syaoran even dare to lay a finger on him, he is condemning the girls to certain death.
With a furious glare, Syaoran gets up, his resolve to defeat the Ryanban firm. The Ryanban cowers, summoning a crowd of the townspeople as buffer from Syaoran's rage. He dares the boy to attack these innocent people... will Syaoran be able to get past them to get to him?