TV-Series
Description
Keisuke Miyauchi is a third-year student at Seidou High School and serves as the team's secondary catcher, wearing uniform number 12. Physically, he has a robust and thoroughly trained body, standing 176 centimeters tall and weighing 80 kilograms. He was born on August 31st and is from Saitama Prefecture.

As a personality, Miyauchi is a man of few words, known for being quiet and speaking only to convey the most important points in the shortest way possible. He is a silent and persistent trainer, dedicating himself to physical conditioning, particularly muscle training. He has a few distinctive quirks: to fire up the team or give a spirited shout, he blows his nose forcefully like a steam locomotive, and he has a habit of grabbing a pitcher’s crotch as a means to ease their tension, a gesture that is widely disliked by his teammates. His personal preferences include a fondness for unicorn beetles and eating protein-rich foods like chicken breast and egg whites.

Miyauchi’s primary motivation and role within the team is to be a reliable and steady presence behind the plate. He is keenly aware that his game-calling and arm strength are inferior to the prodigious first-year catcher, Kazuya Miyuki. Rather than dwell on this gap, Miyauchi focuses on his own strengths. His greatest asset is his blocking ability; he is resolute in his will to never let a pitch get past him, boasting some of the best defensive fundamentals on the team. He also asserts that Tanba, the team's ace, is the absolute ace, and works to form a stable battery with him and the timid reliever Kawakami.

Key relationships define his role on the team. His relationship with the ace pitcher, Tanba, is built on trust and secret training sessions. With Miyuki, he has a competitive but respectful dynamic; Miyauchi constantly strives to surpass him for the starting catcher position but also admits to himself that he cannot match Miyuki's overall talent. His physical strength and blocking skills earn him the nickname muscle senior from the first-year pitcher Eijun Sawamura.

Miyauchi's development is rooted in perseverance rather than natural brilliance. Like many of his third-year classmates, including captain Tetsuya Yuki and Jun Isashiki, Miyauchi was considered a weak player during his first year of high school. Through persistent, silent hard work and training over three years, he molded his physique and skills to become a dependable catcher capable of easily handling the explosive fastballs of pitchers like the rookie Satoru Furuya. His notable abilities lie in his physical strength, mental fortitude, and defensive catching skills, which are considered high, even if his overall sense as a catcher is not as sharp as Miyuki's.