Wakana is Seimei’s wife and Yoshimasa’s mother. She died when he was only two years old due to an illness. Although she died a long time ago, her spirit hasn’t cross to the other side.

Masahiro also met her for the first time in the final episode and not knowing that she’s his grandmother. He met her in the spirit world when he was ready to cross over to the other side, and she invites Masahiro to sit beside her. There she tells him that her lover hasn’t come and that’s the reason why she couldn’t cross to the other side just yet.

Wakana also reminded Masahiro of the person that is precious to him and managed to persuade him to return.

(Source: Wikipedia)