Kimi to Boku wo Tsunagumono

After getting hit in the head, Asakawa Mayu, the beautiful classmate of Date Asahi, regains her memories from her past life as an old man in the service of a young master—and Date happens to be that young master's reincarnation! Following these strange events, Asakawa now begins to search for Date's fiance from his previous life. The relationship between this servant and young master will gradually change.

(Source: Hametsu no Megami Scans)