You're Wonderful, Sakura-chan! Tomoyo's Cardcaptor Sakura Video Diary Special! is the third OVA of the anime series of Cardcaptor Sakura.
Sakura and her friends overhear Yamazaki saying that in addition to the usual red mailboxes, there are blue ones too. Everyone assumes it is just one of his usual lies, but Sakura and her friends come across a blue mailbox after school. Meilin recalls Yamazaki opening his eyes while telling the story, and this is confirmed after a look at the video tape Tomoyo was recording of Sakura at the time. Meilin realizes that Yamazaki must only tell the truth when he opens his eyes. They rush outside when they hear Yamazaki and Chiharu coming, and watch as, while his eyes are open, Yamazaki says that if someone mails a letter towards someone he or she loves in the blue mailbox, that person will love them too. Sakura, Syaoran and Meilin go to write letters, and it is revealed later on that Yamazaki was only opening his eyes because Chiharu stepped on his foot, and the mailbox was blue because of a spilled paint can. Not knowing this, Sakura, Syaoran and Meilin fight over who gets to mail their letter first while Tomoyo records it. Chronologically, this takes place some time between episodes 20 and and 43.