The fight went to a decision, and the judges gave Hasegawa a 3–0 victory, ending Sahaprom's long reign over the bantamweight division.

However, Morales backed out of the fight due to an injury, and the eighth-ranked contender, Geraldo Martinez, was hastily called up as a substitute.

Hasegawa put Martinez down again early in the 7th with a dazzling left straight, and the fight erupted into a massive slugfest between the two fighters.

Hasegawa managed to knock down Garcia again in the 8th, though his own face was covered with blood, and his eye was practically sealed shut from the cut.

Hasegawa fought undefeated challenger Simpiwe Vetyeka of South Africa on May 3, 2007, for the fourth defense of his title.

Very little was known about the challenger, Vetyeka, except that he had an undefeated record (16-0-0), and had defended the South African bantamweight title five times, winning four of those fights by knockout.

Both Hasegawa and Vetyeka wanted to land counter punches, leading to a great deal of inactivity from both sides.

There was some frustration after the fight, because both Hasegawa and Vetyeka complained that one of the advertisements in the middle of the ring was causing their feet to slip.

Hasegawa defended his title for the fifth time on January 10, 2008, with a 12-round unanimous decision victory against top-ranked WBC contender Simone Maludrottu.

Hasegawa had transferred to the newly established Shinsei Boxing Gym in Kobe along with its founder and his trainer, Masato Yamashita, during the 8-month layoff since his last defense.

Hasegawa fought on October 16, 2008, when he defended his title for the 7th time by taking on Mexican prospect Alejandro Valdez.

In the fourth round Montiel landed an attack on Hasegawa, leaving the hometown fighter vulnerable for more blows.

[13] Hasegawa was slated to make his return to the ring against the undefeated Mexican featherweight Carlos Felipe Felix on December 17, 2011.

He had suffered from lack of motivation to continue fighting during the two years after the death of his dearest mother and the tragedy of the aftermath of the 2011 Tōhoku earthquake and tsunami that struck Japan.

[19] Hasegawa fought for the IBF super-bantamweight title against reigning champion Kiko Martinez on April 23, 2014 in Osaka.

In what many thought to be the last fight in the colorful career of Hasegawa, a back and forth contest erupted, with the Spaniard's one punch knockout power being the deciding factor as he urged a referee stoppage in 7th round following a brutal attack on his Japanese foe.