By Jake Donovan

Shinsuke Yamanaka makes the fifth defense of his bantamweight belt, as he faces Alberto Guevara in their main event Sunday afternoon in Tokyo, Japan.

A separate report of the main event will come elsewhere on Boxingscene.com

GONZALEZ WINS BIG, EYES TITLE SHOT

A calculated risk by Roman 'Chocolatito' Gonzalez to vacate one title in pursuit of another is slowly paying dividends. The unbeaten former two-division titlist dropped Oscar Blanquet twice en route to a second round stoppage in the evening's co-feature.

Gonzalez opted to give up his 108 lb. belt following last year's 12-round war with Juan Francisco Estrada, in pursuit of a flyweight crown. For the moment, it appears that his power has followed him up the scales, scoring a knockdown in the opening frame before finishing off Blanquet one round later.

The official time was 0:27 of round two.

Gonzalez improves to 37-0 (32KO) with the win, his third since moving up to flyweight earlier this year. The rising young star is in good company in the division; Estrada moved up as well, upsetting Brian Viloria to become - and still serve as - a unified flyweight titlist.

Blanquet has now lost three straight, including a failed bid versus lineal flyweight king Akira Yaegashi this past summer. The Mexican journeyman falls to 32-7-1 (23KO).

As for Gonzalez' next move at flyweight, his options could prove limited.

Rumor has it that Kazuto Ioka is prepared to dump his 108 lb. title in favor of a move up to flyweight as well. A long awaited battle between Ioka and Gonzalez could be the more realistic option for 2014; Estrada's next challenge will come against Giovani Segura, who knocked out Hernan 'Tyson' Marquez in their Fight-of-the-Year entrant one weekend ago in Mexico.

Another option is Argentina's Juan Carlos Reveco, an alphabet titlist whom Gonzalez called out after the fight. The fight could do big business (relatively speaking to the flyweight division) in South America, given Gonzalez' relationship with the WBA, who recognizes Reveco as one of its many, many titlists.

UNDERCARD

Jorge Linares picked up his fourth straight win, making quick work of Francisco Contreras in their lightweight bout.

A counter right hand put the visiting Dominican down towards the end of the opening round. The bell erroneously sounded despite the round having not yet come to an end, with the referee deeming Contreras (21-4, 16KO) unfit to continue.

The official time was - bizarrely - 3:08 of round one.

Linares caps a bounce back 2013 campaign with three knockouts in as many fights on the year. The former two-division titlist improves to 35-3 (23KO), with his sights firmly set on a title shot in his third weight class.

Takahiro Aoh (25-3, 12KO) scored his quickest win in nearly nine years, stopping Edgar Lomeli in the opening round of their lightweight contest. The former 130 lb. titlist has now scored two straight knockouts since losing his belt in a shocker to Gamaliel Diaz last October.

All of the aforementioned bouts air live on WOWOW in Japan.

Jake Donovan is the Managing Editor of Boxingscene.com, as well as the Records Keeper for the Transnational Boxing Ratings Board and a member of Boxing Writers Association of America. Twitter: @JakeNDaBox