Prequel vignettes to the Kemurikusa TV series released on Tatsuki's official Twitter. They have an irregular episode count as follows: ep 0 (actually unnumbered), 0.5, 0.6, 0.7, 0.8, and 0.9.
After the Kumurikusa TV series finished airing, Tatsuki released another vignette the following week numbered ep 12.1 both on his Twitter account and official YouTube channel.