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.

This take was written by generative AI, one per person, from publicly reported facts (editorial policy). It is a reading of the record, not reporting.

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. He went from Meioh High School in Akita to the Chiba Lotte Marines in the fourth round of the 2018 draft and made his first-team debut in 2021.

Name (English)

Koki Yamaguchi

Name (Japanese)

山口航輝

Reading

やまぐち こうき

Born

August 18, 2000 (age 26)

Origin

Osaka City, Osaka Prefecture, Japan

Occupation

Baseball player

Zodiac / Chinese zodiac

Leo / Dragon

• Instagramhttps://www.instagram.com/51marines/
• Wikipedia (Japanese)https://ja.wikipedia.org/wiki/%E5%B1%B1%E5%8F%A3%E8%88%AA%E8%BC%9D
• Wikidatahttps://www.wikidata.org/wiki/Q65095763

Tags

• From Osaka Prefecture
• Baseball player

Last updated

October 18, 2026

Only publicly available facts are listed; non-public or unconfirmed items are omitted. Base data was compiled from Wikidata from June 2026 onward; ages are recalculated daily and deaths are checked against Wikidata on an ongoing basis. English text is machine-assisted (facts translated by Sonnet, "My Take" written by Opus 4.8). The Japanese page is the source of record.