Gyakkou-saki ga (Moto) Konyakusha no Naka tte Douiu Koto desu ka? Konyaku Haki sareta noni "Karada no Naka" de Dousei suru Koto ni Narimashita

Alicia, daughter of a count, was told that her fiancé wants to call off their engagement. One year later, she was killed by his new fiancée... and next moment, she found herself inside the ex-fiancé!? Alicia thought she died after being pushed and falling off the long stairs. However, when she woke up she was "inside" the body of her ex-fiancé, Gilbert. It turns out that her soul went back time before her engagement was called off and found a place inside Gilbert, along with his own soul. Gilbert was the one who suddenly dumped her and got engaged to Cordelia shortly after. Knowing that "Alicia (past)" is still living, Alicia decides to find evidence that Gilbert was having an affair and make "Alicia (past)" call off the engagement herself before he tries to. She starts her investigation, but why does it seem that Gilbert is in love with Alicia!? And why did Cordelia try to kill her? An awkward, unique love story with two souls in one body! (Source: Kadokawa)