Kyojin no Samurai Honou(1979)

One day, at the Giants' Tamagawa ground, Egawa was throwing a simulated game in front of Manager Nagashima, when suddenly a stranger stepped into the box and mowed down Egawa's pitches. His name is Hono Mizuki. He was a player who had to move from one school to another due to his short temper getting into fights, so he never caught the eye of any scouts despite his outstanding ability. Osamu Sawada, a freelance talent scout, was asked by Manager Nagashima to investigate. He tested Mizuki first against Hyuma Hoshi, and then Mitsuru Hanagata and Hosaku Samon both had trouble hitting Mizuki's pitches, showing that he had pro-level stuff. Mizuki's competitive spirit is reignited. Mizuki and his best friend set their sights on joining the ranks of pro baseball together.

(Source: Amazon.jp, translated)

Note: Release date information are based on the tankoubon volumes.