Kaja Bergmann  

, カヤ バーグマン

In Arashis era, there was another ghost who was friends with him. This ghost came from Germany and studied at his school. Although she had a calm and composed demeanor like Arashis, her personality was completely different - more reserved and serious compared to his lively and carefree nature. She also shared the same time-traveling abilities as him, but there was one significant difference: she could only connect with living girls.