According to the official website, the story arc for Tachibana Miya and Kamizaki Risa will be included in the 13th Blu-ray/DVD volume for Amagami SS. Besides, both arcs will receive their own ending theme.
People who watches Amagami SS for Miya will be cheering since Miya will get her own arc. Oh wait, doesn’t it means that it will be an incest arc. ZOMFG! And who is Risa? According to MAL, she is Junichi’s secret, yandere stalker. Oh shit! Will there be a nice boat scene? We will have to wait to find out. XD
Source: Anime News Network