According to the official website, an unaired episode of Amagami SS+ plus
was announced to be released in the seventh volume of the Blu-ray on October 3rd. It's Tachibana Miya
's arc titled "Onsen (hot spring)".
In the episode, Junichi hasn't gone around with any girls yet. Miya goes to a hot spring with Sae and Ai. There she meets Tsukasa, Rihoko, Kaoru and Haruka. The main characters except Junichi enjoy girls' talk in the hot spring.
Source: Amagami official website
Amagami SS+ plus: Onsen