A Touhou comic series by Asamura Hiori, spun-off from Touhou Crimson Wing Book (pool #822).

Satori has seemingly fallen in love with Rinnosuke. However, she may have some competition for his affections. This is interspersed with Rinnosuke's flashbacks to the time he spent with Sendai Hakurei no Miko.

Now a series of videos on NicoNicoDouga: http://www.nicovideo.jp/mylist/16375099.