(from ebookjapan):

Fourteen years ago, Natsuko lost her father in an accident, and she was the queen of the crystal world, Oxtan Ryunka!　

Seven Bridge, a group of seven mechanical creatures, not fairies, stand up to the threat of Cunningham, a rabbit-faced man, Bookman, a splitting man, and the Nuclear King, who aims for supremacy over all the worlds. Now, let's go on an adventure through seven parallel worlds!　

A full-length SF adventure by the genius of the Japanese SF world, Shuho Itabashi!