Mikura, Kurokawa, and Harada are the 3 members of the Danger Service Agency (DSA). Mikura is the brawns of the group, Harada is the brains, and Kurokawa is just a bitter ex-cop that likes to think he's in charge. They'll take on any job as long as it involves lots of danger and, of course, money. If you want to live long enough to eat dinner, you better not cross them. Their biggest case, however, could prove to be finding out why someone wants Kurokawa assassinated.
Three sisters, Hozuki, Kazuki, and Hazuki, are descendants of Galileo and have completely different personalities and tastes; they never meet eye-to-eye. One day the girls are suddenly attacked by a mysterious organisation. The organisation was after the Galileo Tesoro which Galileo Galilei was said to have discovered. Still unaware of what was going on, the sisters escape on the airship they built after the sudden attack. But it won't be so easy for these three sisters to help each other out in a pinch when they're constantly at odds with each other.What is the Tesoro, and what is the organisation after? And what about the relationship between the sisters?