Enzai Reijou wa Shinjitai: Ginpatsu ga Fukitsu to Iwarete Kon'yaku Haki Sareta Shishaku Reijou wa Ansatsu Kizoku ni Dekiai Sarete Daini no Jinsei o Tannou Suru You desu

Betrayal and false accusation lead to a contract marriage between a doting assassin and a falsely accused young lady!? Airi is betrayed and falsely accused by her fiance and best friend. At the bottom of despair, another assassin is sent to kill her. However, instead of killing her, the assassin proposes a contract to become her "fake wife."

(Source: Pixiv Comic, translated)