A collection of 4 short side stories.
The first one tells about the events of a decade ago, when Yoshiyuki was adopted by Asakura family.
From the second story we'll learn how Yoshiyuki became friends with Wataru and Suginami, and how the Setsugekka trio was formed.
The third story is about a close friendship of Miki and Mahiru, when she was still alive.
The fourth story is an alternate reality, which tells how in one rainy day Sakurai picked up a broken "μ", who was thrown out by heartless owner, and how strongly he became attached to her.