A story about me advancing in the demon army and winning the heart of the Demon King's daughter (or so it was supposed to be)

*Regardless of the setting, fundamentally, this is a story of one warrior's rise to prominence. Naoya Matsuura, a second-year middle school student, is suddenly transported to another world, where he is told the unreasonable thing: "You will be assigned to the direct military unit of the princess (the Demon King's daughter) and made a soldier." However, by chance he comes face-to-face with the said "Demon King's daughter," and Naoya accidentally falls for her delicate charm. Naoya, who survived one year of fierce battles as a "meat shield" (slave soldier), is set to gradually gain prominence in the demon world (supposedly). ☆Updated with a bonus chapter on September 27, 2017. Please feel free to read it.*