[4] Yamanaka became interested in the sport of boxing as a result of seeing the likes Joichiro Tatsuyoshi, Mike Tyson, and Naseem Hamed on TV.

[6] Yamanaka trains at the storied Teiken Gym in Tokyo under former pro boxer and Japanese nation champion Yamato Shin.

[5] Yamanaka captured the vacant WBC bantamweight title in his first world title shot against Mexico's Christian Esquivel via an eleventh-round technical knockout after knocking him down in the sixth and eleventh rounds at the Yoyogi National Stadium Second Gymnasium in Tokyo on November 6, 2011.

Darchinyan had unsuccessfully attempted to become a 3-weight world champion twice before, losing by decision to Abner Mares and Anselmo Moreno.

[5][12] Yamanaka defended his title once more in 2012 against Tomas Rojas, knocking the former WBC super flyweight champion out in the 7th round with a left-hand cross.

Yamanaka would end up winning by technical knockout on the 12th round after knocking Tuñacao down three times in the course of the fight.

Yamanaka dropped Sor Rungvisai 3 times but was unable to finish him, winning by unanimous decision (116-108, 115–109, 114–110) but ending a 5 fight knockout-streak.

Yamanaka would run into his toughest fight yet in his ninth title defense against former WBA champion Anselmo Moreno.

Moreno, a classical out-boxer, kept Yamanaka from landing his signature left-hand using his jab and movement to neutralize the WBC champion.

Both fighters would continue trading punches until the final bell, but Yamanaka had dominated most of the fight and he was given a unanimous decision (117-107, 117–107, 117–107).

[19] On March 2, 2017, Yamanaka fought overmatched opponent Carlos Carlson to a seventh-round TKO win.

With this fight, Yamanaka sought to equal Yoko Gushiken's record for most successful defenses by a Japanese world champion.

In a press conference after the fight, Yamanaka stated that he was unhappy with the stoppage but he didn't blame his trainers for it.

[24] Following Nery testing positive for zilpaterol, a banned substance, The Ring reinstated Yamanaka as their bantamweight champion.

Despite cutting two pounds before the final weigh-in, he was stripped of his title prior to the bout for failing to make weight.