Harland Defense is an old man. He holds the world’s only Risk Rarity Level 8 rating,and even that doesn't fully express the overwhelming power of this one-of-a-kind hitman. He takes on missions from governments and the most influential people in the world,receiving weapons from a girl known as “Mourning Dress” and executing each job precisely and perfectly. “I want to create a world without crime.” The greatest hitman had only one small weakness. That weakness was the peaceful, troubled girls with a story behind them who lived in the apartment building where Harland worked as the apartment Manager. A thrilling yet heartfelt story unfolds in the hitman’s life,filled with both secret missions and charming everyday moments with girls who have stories of their own. (Source: Manga Mirai) A completely new vertical-reading color comic by Kamaitachi Kazuma, the author of ‘A Certain Magical Index’ and ‘A Certain Scientific Railgun’!

The story takes place in the second half of the 19th century, as Japanese culture gains popularity in the West. A young Japanese girl, Yune, accompanies a French traveller, Oscar, on his journey back to France, and offers to help at the family's ironwork shop in Paris. Oscar's nephew and shopowner Claude reluctantly accepts to take care of Yune, and we learn how those two, who have so little in common, get to understand each other and live together in the Paris of the 1800s.