Haruka na Sora is the fandisc (extra content by the producers) of Yosuga no Sora, it contains the routes of Kozue, Yahiro and Sora (Sequel for her main route in the Visual Novel) plus short scenarios such as karaoke route and the characters introduction. The name of the routes are:
"I am in love with her even though she's a rigid chairman." (堅物な委員長だって恋するのです。) for Kozue,
"We are incompatible? (相性が悪い二人？) for Yahiro,
"The end of Azure." (蒼穹の果てに。) for Sora and "Let me hear your song." (君の歌を聴かせて。) for Karaoke.