The "bond" in the title is often ironic. In this specific arc, the resolution typically reveals that the darkness within the client is just as dangerous as the target they wished to kill. Usobuki often leaves his clients in a state far more sorrowful or broken than when they started. Why It Resonates

The manga centers on , a mysterious man in a black suit with piercing crimson eyes. He is an assassin who never technically "kills" his targets. Instead, he uses the "power of suggestion" to manipulate his victims' thoughts, leading them to their own deaths through suicide or carefully orchestrated accidents. Because there is no physical evidence or direct action, his crimes are considered "impossible to prosecute" . Chapter 41: "The Bond Between Husband and Wife (Part 2)"

You can find the full chapter and the rest of the series through readers like MangaDex or Anime-Planet. 1 | Chapter 41 - Funouhan - MangaDex

While the client usually wants someone eliminated "free-of-charge," Usobuki’s true payment is witnessing the "folly of humankind".