My Lovey-Dovey Wife Is a Stone Cold Killer

• Ja Kanji — 拝啓…殺し屋さんと結婚しました • Ja Romaji — Haikei... Koroshiya-san to Kekkon Shimashita • Genre — Romantic comedy

• Author — Donten Kōsaka • Publisher — Media Factory • Imprint — MFC Cune Series • Magazine — Comic Cune • First — September 27, 2019 • Volumes — 8 My Lovey-Dovey Wife Is a Stone Cold Killer, also known as Dear Sir... I Married a Killer, is a Japanese manga series written and illustrated by Donten Kōsaka. It began serialization in Media Factory's Comic Cune magazine in September 2019, and has been compiled into eight volumes as of September 2025. The series is licensed in North America by Seven Seas Entertainment.

The series follows a salaryman who recently married Setsuna, a professional assassin. Having only dated for a short time prior to their marriage, he is surprised to learn of her background. Despite this, he comes to accept her work. The story follows the couple as they balance married life with Setsuna's job as a hitman.

• Husband • Yūya Hirose (voice comic) • The unnamed protagonist, he is a salaryman who met Setsuna after they were introduced by a mutual friend. Because they only met a few times before they started dating, he did not know about her job as an assassin. Although they are already a couple, he is still not used to married life. • Setsuna • Marika Kōno (voice comic) • A professional assassin who had just recently married. She met her husband after their mutual friend invited them to a drinking party. She is proficient both as a hitman and at household chores. Because of her work, she assumes a cold personality, although she warms up as her relationship with her husband develops. • Otonari-san • Mai Fuchigami (voice comic) • Setsuna and her husband's next-door neighbor. Her name is a play on the Japanese word for next-door neighbor, otonari-san.

The series is written and illustrated by Donten Kōsaka. It began serialization in the November 2019 issue of Media Factory's Comic Cune magazine, released on September 27, 2019. The first tankōbon was released on May 27, 2020. The series has been compiled into eight volumes as of September 27, 2025. A voice comic was posted on YouTube on September 27, 2021, to commemorate the release of the third volume. The series is licensed in North America by Seven Seas Entertainment, with the first English volume being released on November 23, 2021.

My Lovey-Dovey Wife Is a Stone Cold Killer is classed in the genre romantic comedy anime and manga. Associated with Japan.