Oguni made his pro debut on November 8, 2009, winning his first ten fights before losing to his countryman Shingo Wake in 2013 for the OPBF super bantamweight title.

On his first title bout Oguni was a considerable underdog heading into the bout against Dominican's world champion Jonathan Guzmán, yet Oguni's rode an adrenaline rush all the way to the final round, forcing Guzman to overcome an opening round knockdown and a mid-round cut to prevail by identical scores of 115-112.

Oguni pulled off a stunning upset outpointing Jonathan Guzman to win the IBF Super bantamweight title on December 31, 2016 in Kyoto, Japan.

[1][2] Oguni will be making his comeback by taking on Filipino's three division world champion John Riel Casimero on October 12, 2023, at the Ariake Arena in Tokyo, Japan.

[3] The bout ended with a controversial technical draw because of an accidental headbutt.