Eiichi Yamagishi

Eiichi Yamagishi is the alter-ego of epomynous mangaka Eiichi Yamagishi, an assistant of Gouushou Aoyama who appears in several of his series. He's known to most Detective Conan fans as the manager of Youko Okino, who's also based on a mangaka and past senior student of Goushou and Eiichi from the Ekoda Campus of Nihon University. He also got cameos in other Goushou works, like WALK MAN, Magic Kaito, Yaiba and 3rd Base 4th, additionally to the spin-offs Zero's Tea Time and Hanzawa the Criminal, made by other people.

(Source: Detective Conan Wiki)