This first OAV covers the volume 22; meaning from their arrival to Nihon Country (Kurogane's home world) up to 'Syaoran' encounter with princess Sakura, Watanuki and CloneSyaoran inside the Dream World.
We also got random flashbacks here and there about what happened in Celes.

Note: The story between the first and the second OVA is covered in volumes 18-21 of the original manga.

AniDB | ANN | MAL | TVDB

Prequel: Tsubasa Tokyo Revelations
Other: xxxHOLiC Shunmuki