"Oikakekko wa Yume no Naka" tells the story of how Ren and his childhood friend play hide-and-seek. No matter how hard she tries to hide, Ren would always somehow find her, for some reason. It is an innocent song despite everything that had happened in Karakuri卍Burst; if this has anything to do with Suzunosuke's doujinshi, this could probably have happened not long after they became friends.
It was merely a dream, however. The "flashback" of two kids playing hide-and-seek disappeared; instead, they "pulled a trigger". It was a nightmare. Until the nightmare ends, Tsubaki bids good night.
This song is the third song in the Karakuri Series, and it was released on the Karakuri卍Burst album.