Shinozaki-kun no Mente Jijou

A regular salaryman named Shinozaki, who has been experiencing neck pain, has his routine life disrupted by a woman named Yuuyake. She claims her grandmother, a magician, altered his body significantly, turning it into a mechanical one that needs ongoing maintenance. Yuuyake takes on the responsibility of maintaining his internal machinery. His new life involves interactions with Yuuyake and a mysterious being named Grey. The story spans 43 main chapters, one epilogue, and 14 additional chapters.