Clannad

Until the End of the Dream (1x9)

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Tomoya, Nagisa, and Fuko spend the night at school having a pre-celebration for Youko's wedding. In the morning, Tomoya and Nagisa have forgotten about Fuko and cannot see her. Both Tomoya and Nagisa later feel that there is something important that they are forgetting, and finally remember about Youko's wedding, which is also when they are able to see Fuko again. On the wedding day, initially the only students to arrive were Tomoya, Nagisa, and Fuko, but after the ceremony it is shown that everyone who had received a starfish came to the wedding. Fuko ultimately disappears after thanking Tomoya and Nagisa for what they have done, and congratulating her older sister. A rumor still persists at Tomoya's school of Fuko as a cute girl who is constantly running through the school.