Arima began playing baseball in the first grade of elementary school. He joined a local youth baseball team and later played for his junior high school’s rubber-ball baseball team. He then went to Aichi Institute of Technology Meiden High School, a baseball powerhouse that has produced numerous professional players. Until his second year of high school, Arima primarily played as an outfielder, batting fifth and playing right field. At the time, he planned to continue his studies rather than pursue a professional career, which did not seem like a realistic path at that time.

“The player I aimed to be like back then was Katsuki Azuma, a pitcher for the Yokohama DeNA BayStars. While looking for universities in the Kansai region, I decided to apply to Ritsumeikan University, which also happened to be Azuma’s alma mater, and I was given the opportunity to participate in tryouts.”.

From the winter of his second year of high school, Arima began to stand out as a pitcher through intensive training. In the summer of his third year, he led his team as their ace pitcher to the National High School Baseball Championship (Summer Koshien). After enrolling at university, he made the bench from the spring of his first year, and in the fall of his second year, he recorded his first collegiate victory against Kansai University.

In his third year at university, Arima received the Outstanding Pitcher Award in the 2025 Kansai Big 6 League Spring Season and was also selected for the Samurai Japan Collegiate National Team that competed in the 45th Japan–USA Collegiate Baseball Championship Series. Meanwhile, the Ritsumeikan University Baseball Team claimed a dramatic walk-off victory in the 2025 Kansai Big 6 League Fall Season, securing its first league title in six and a half years. Despite the team’s success, however, Arima says the Fall League season was far from smooth sailing for him personally.

“The team was making great strides, but even when I pitched, I didn’t feel like I was really contributing to the team’s wins, and that sense of frustration kept growing. I consulted with our trainer to revisit my pitching form and training regimen, and I spent a lot of time thinking things through on my own.”

He recalls that he was finally able to break through during the third game of the Kansai Regional Qualifying Round for the 56th Meiji Jingu Baseball Tournament. Shortly after winning the Fall League, he had the opportunity to speak with Shigetoshi Hasegawa, a Ritsumeikan University alum who played for Japan’s Orix BlueWave and later Major League Baseball in the United States*. The two continued to stay in touch, and Arima says Hasegawa’s advice after the first game of the regional qualifier made a significant impact on him.

“He told me to take deep breaths and to picture myself at my very best. That advice on mental training really resonated with me. Once my mind cleared up, I started pitching better.”

Then came the opening game of the Meiji Jingu Baseball Tournament. Arima says he could feel that he was in excellent form that day. He went on to set a new tournament record with 10 consecutive strikeouts, becoming a key player in Ritsumeikan’s impressive run.

*For more details, see “ Discussing Dreams of Pro Baseball: A Conversation between Ritsumeikan Baseball Team Pitcher Gaku Arima and Former MLB Pitcher and Ritsumeikan Alum Shigetoshi Hasegawa.（Japanese Only） ”

After overcoming strong opponents in the second round, Ritsumeikan entered the final with the team morale running high as they pushed toward a national championship. Although their opponent in the final appeared stronger on paper when comparing individual players, the Ritsumeikan team had the momentum. “We’re going to win it all,” they told each other as they took the field for the final game. In the end, however, it was the opposing team that prevailed in a tense pitcher’s duel. As soon as their runner-up finish was decided, Arima stood on the field, his gaze fixed on the opposing players celebrating on the mound. What was going through his mind at that moment?

“The Ritsumeikan University Baseball Team, with more than a 100-year history, achieved its first runner-up finish since the team was founded. But personally, more than happiness, what I felt was frustration. I kept looking at the other team so I could picture the vision I wanted to realize the most. I burned that scene into my mind and told myself, ‘Next year, I’ll be the one standing there. Next time we’ll be national champions, and I’ll be sharing that moment of victory on the mound with my teammates.’”

“Picture yourself at your very best.”
Just as Arima had practiced visualization after receiving this advice from Shigetoshi Hasegawa, the moment the team finished as runners-up, he had already begun envisioning the future that lay ahead.

Next year will be Arima’s fourth and final year as a university student, marking the last season of his collegiate playing career. With the most senior members about to graduate, the team’s new lineup is preparing to begin its next chapter, and Arima’s goals are clear.

“Next season, the goal of the Ritsumeikan University Baseball Team is to realize our long-held dream of becoming the number one team in Japan. And on a personal level, my ultimate goal is to go pro. I want to perform well next season and develop into the kind of player who can be selected in the first round of the draft,” he states emphatically. Arima approaches baseball with sincerity, and he puts his heart into every pitch when he is on the mound. As he steadily works toward achieving his goals, his journey is one well worth keeping an eye on.