"Blue Door" is a 4-song EP by Minchanbaby and Anna Fujishiro, including the previously released single "Yaruko and Yaruko". Executive produced by Minchanbaby. The EP was produced over a long period of time after Anna Fujishiro's marriage and childbirth, and includes three new songs: the nostalgic pop song "Blue Door", the bright pop punk "I see, the world.", and "sunflower", dedicated to Anna Fujishiro's dog, who passed away.