Akasaka Yukie is Akasaka Mamoru's wife, and is only seen in Himatsubushi-hen and at the end of Matsuribayashi-hen. In that chapter she stays in the hospital while she is pregnant. While in the hospital, she falls from the stairs and dies but her baby survives. In Minagoroshi-hen and Matsuribayashi-hen however, it is revealed in these alternate timelines that Mamoru returned early after heeding Furude Rika's warning, thus preventing her death.

(Source: Higurashi No Naku Koro Ni Wikia)