Shinozaki-kun no Maintenance Jijou

Shinozaki, an ordinary office worker recently worried about being "off his head," is approached by a woman named Yuyake. She explains that her magician grandmother modified his body in the past... causing him to have a lot of inside machinery?! He'll have to receive internal maintenance from Yuyake...

A slightly wobbly magical remodeling life between a very ordinary salaryman, Shinozaki, and an enigmatic magician, Yuyake, begins.

(Source: Kadokawa, translated)