[10] Having started out as a striker, Mikuni began playing as a center back in his third and final year of high school.

[12] In 2018, Mikuni helped the Aomori Yamada win Sanix Cup International Youth Tournament and National High School Soccer Championship Final.

[18] In a follow–up match against V-Varen Nagasaki, Mikuni made an improvement in his second appearance for Avispa Fukuoka when he helped the club kept a clean sheet, in a 0–0 draw.

[19] After missing two matches due to an injury, Mikuni returned to the starting line–up against Albirex Niigata and kept another clean, in a 2–0 win on 23 March 2019.

[22] He previously played uncharacteristically, such as, losing possessions and giving away the ball that saw him substituted at half time, in a 1–1 draw against Yokohama FC on 7 April 2019.

[23] After two months away, Mikuni made his first appearance for Avispa Fukuoka, playing 120 minutes, in a 2–1 win against Kagoshima United in the second round of the Emperor’s Cup.

[28] In a match between Avispa Fukuoka and Mito HollyHock on 4 November 2020, Mikuni played briefly against his older brother, SteviaEgbus when he came on as a late substitute, as the club won 1–0.

Following his loan spell, Mikuni made his first appearance of the 2022 season for Avispa Fukuoka, starting a match and played 82 minutes, in a 1–0 loss against Yokohama F. Marinos on 10 September 2022.

[36] Throughout the 2023 season, Mikuni made only twelve starts for Avispa and found his playing time mostly confined to the substitute bench.

[38] In a match against Vissel Kobe on 25 June 2023, Mikuni suffered an injury and was substituted in the 39th minute, as Avispa Fukuoka lost 3–0.

[39] After being sidelined for three months, he returned from injury, coming on as a 51st minute substitute, in a 2–0 win against FC Tokyo, as the club advanced to the semi–finals of the J.

League Cup against Nagoya Grampus, as he helped the club won 2–0 on aggregate to advance to the final.

[41] However, he was left out of the squad in the J.League Cup final, as Avispa Fukuoka won 2–1 against Urawa Red Diamonds to win the tournament.

[61][52] Mikuni was born in the United States to a Nigerian father and a Japanese mother, and raised in Higashimurayama, a semi-rural western suburb of Tokyo.