In an alternate Tokyo of 1969, thirteen-year-old Marin suddenly becomes the target of mechanical assassins. The armoured Melan Blue appears to protect her, without providing an easy explanation for what is happening. Their connection brings an ordinary neighbourhood into contact with an unfamiliar world above it.
Marin needs someone who can keep her alive, but protection is only the beginning of a relationship. Melan is a living weapon with purposes and obligations outside her experience. The story places their growing dependence beside the attachments and hardships that already shape her life.
The difference in scale between Marin and Melan makes their first connection visibly unequal. She cannot meet an armed attack with comparable force. What develops between them must therefore involve understanding and trust as well as physical protection, giving the extraordinary figure a place inside a recognisable human life.