Kono Koi, Omamori Moushi Ageru

A samurai and a princess have been reincarnated as the opposite gender!? Haruna Tokiko is beautiful, capable, kind-hearted, and dignified, earning her respect from those around her. She's a modern-day woman with memories of her past life as a male samurai. One day, Mizuki Sasaoka joins the company mid-career and turns out to be the unmistakable reincarnation of the princess she adores! Tokiko is thrilled to be reunited with her beloved in this life, only to discover that her beloved princess has been reincarnated as a boy...!? (Source: Shogakukan, translated)