According to the official website, the voice cast of the new OVA Aki-Sora: Yume no Naka was changed from that of the previous one.

Cast of Aki-Sora Yume no Naka the previous seiyu are in the parentheses.
Aoi Sora: Shiroi Kumo (Kinoshita Sayaka)
Aoi Aki: Natsuno Kohri (Kawaragi Shiho)
Aoi Nami: Shirayuki Modori (Ueda Kana)
Sumiya Kana: Gogyo Nazuna (Okajima Tae)

Shiroi Kumo (or Shirai Kumo) and Shirayuki Modori are presumably assumed names. Natsuno Kohri and Gogyo Nazuna mainly play roles in adult games.

Aki-Sora producers asked Niconico Douga to stream the first volume of the OVA for the PR but Niconico refused the offer.

Source: Aki-Sora official website
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