Clannad - Season 2 Episode 6 Forever by Your Side

After getting over Igarashi, Misae starts hanging out with Katsuki more and starts falling in love with him. One day, Katsuki realizes after going to his house with two of Misae's friends that he is in fact not Katsuki Shima, but a cat who was sent by the dying Katsuki Shima to grant Misae's wish. At the autumn festival, Misae confesses she has come to love Katsuki, but that night he disappears shortly after Misae made her wish for him to always be with her. After Tomoya wakes up, and realizes the cat showed him all this, Tomoya later tells Misae some things Katsuki did not get a chance to tell her.