Your and My Secret(2005)

Your and My Secret is a Japanese anime series that follows Akira Uehara, a timid high school student secretly infatuated with Nanako Momoi—a girl who appears delicate until she speaks, revealing a violent and aggressive personality. When Akira visits Nanako's house, her eccentric grandfather forces him into an experimental machine. Nanako gets caught in the blast, and the two swap bodies. Desperate to stay in Akira's gentler form, Nanako sabotages the machine, leaving them with a massive 2-million-yen repair bill and no way to reverse the swap. Trapped in each other's lives, the mismatched pair must navigate school, family, and mounting debt while learning to understand one another. The series blends comedy with unexpected character depth as opposites collide.