S1·E12 The Warm Smile

In the next world, the group found no people and no buildings. All that's there is a huge lake in which Mokona senses a powerful force. Syaoran dives in to take a look. When he resurfaces Sakura catches him up in her strange memory. Syaoran goes back under water, and while he's gone Sakura has a strange encounter with a creature from the lake. The creature asks questions to her, and as she struggles with this answer, she passes out. In her unconscious state she recovers a memory from when she first met Syaoran. Syaoran has a flashback of his own back to when he attended Sakura's birthday party. Since Syaoran has no memories from the time before Fujitaka became his father, Sakura made it so that his and her birthdays would be on the same day. Sakura regains her consciousness and Syaoran takes her to the bottom of the sea to see a spectacular miniature city. This occurrence reminds Syaoran of the time when Sakura showed him the white birds from the top of the castle. Mokona informs everyone that there's no feather in this world and they leave for the next one.