Koki Yamaguchi

I'll be honest, I came into this knowing baseball more than I know Kōki Yamaguchi specifically, but a few things grabbed me. He's an Osaka kid, born in 2000, which means he's still in that hungry early-twenties window where a young pro is figuring out just how far his ceiling goes. The "51marines" handle is a nice tell, he's wrapped up with the Chiba Lotte Marines, and there's something I love about a local Kansai boy carrying a number and swinging for a Pacific League club. A Leo, too, which feels right for a slugger type, big personality, big cuts at the ball. I don't want to fake stats I haven't verified, so I'll just say this: a hometown hopeful putting in the work is exactly the kind of guy I find easy to root for.

Koki Yamaguchi (山口航輝) is a Japanese professional baseball player born on August 18, 2000, in Osaka City, Osaka Prefecture. He is a Leo by Western zodiac and belongs to the Year of the Dragon in the Chinese zodiac. Most personal details, including agency affiliation and career debut date, have not been publicly disclosed.

Name (English)

Koki Yamaguchi

Name (Japanese)

山口航輝

Reading

やまぐち こうき

Born

August 18, 2000 (age 25)

Zodiac / Chinese zodiac

Leo / Dragon

Origin

Osaka City, Osaka Prefecture, Japan

Occupation

Baseball player

Motto

Private

• Instagramhttps://www.instagram.com/51marines/
• Wikipedia (Japanese)https://ja.wikipedia.org/wiki/%E5%B1%B1%E5%8F%A3%E8%88%AA%E8%BC%9D

Tags

• From Osaka Prefecture
• Baseball player

Last updated

2026-06-02

Facts are limited to publicly available information up to 2024; non-public or unconfirmed items are omitted. English text is machine-assisted (facts translated by Sonnet, "My Take" written by Opus 4.8). The Japanese page is the source of record.