Takes place during book 7 of TWST Yuika, Grim, Ace, Deuce, Epel, Ortho, and Jack decide to leave Lilia's Farwell party early and check out Yuika's bedroom mirror. Sebek also shows up later while looking for Malleus. But right as Malleus casts his signature spell, a stellaron appears and activates on the Isle of Sages. The combined power of Malleus's spell and the stellaron causes a portal open in Yuika's room and teleportes the group onto Herta Space Station. Now, the group must travel across the stars along with the Astral Express crew in order to find a way back home.