Early career Yamaguchi began playing football in the third grade, playing mostly as an
attacking midfielder. Upon entering junior high, he participated in trials with the
Cerezo Osaka,
Gamba Osaka and
Kyoto Purple Sanga youth academies and ultimately joined the Cerezo Under-15 team, from whom he received an invitation on the spot. He enjoyed steady progress at the club, being selected to be part of the first entering class of the
Japan Football Association Elite Program at the end of his first year. In 2006 Yamaguchi was promoted to the Cerezo Under-18 team, which later won the JFA Prince League U-18 in the 2008 season, in which he served as captain and was named league MVP.
Cerezo Osaka Along with academy teammate
Yusuke Maruhashi, Yamaguchi was promoted to the senior team in 2009, spending three months of the season training with the
Palmeiras Under-21 academy. He was named to the Japan Under-21 team in his second season and played in all of the matches in a gold medal campaign at the
2010 Asian Games in
Guangzhou. Yamaguchi began to receive substantial playing time with Cerezo in 2011, scoring his first league goal on Matchday 24 against
Urawa Reds. The addition of
Fábio Simplício resulted in Yamaguchi being increasingly deployed as an
attacking midfielder toward the latter part of the season, which he finished with 30 appearances. He followed up by winning a regular position on the Cerezo side in 2012, combining with
Takahiro Ogihara in central midfield for both club and country, and being named to the
Under-23 team.
Hannover 96 On 21 December 2015,
Hannover 96 announced that they signed Yamaguchi. Yamaguchi played for Hannover 96 in 2016, however returned to Cerezo Osaka mid-season.
Vissel Kobe On 19 December 2018, Yamaguchi sympathized with the goal of seriously aiming for the J1 League and AFC Champions League and officially completed a transfer to
Vissel Kobe (later, he achieved the league championship as his goal). According to the media, it was a three-year contract with an annual salary of over ¥100,000,000, totaling over ¥400,000,000.
V-Varen Nagasaki On 23 December 2024, Yamaguchi announcement officially transfer to J2 club,
V-Varen Nagasaki from 2025. ==International career==