For Koseki this will be her 14th defence allowing her to break the long standing Japanese national record of the great Yoko Gushiken who defended the WBA Light Flyweight title 13 times in the 1970's and 1980's. Of course female boxing and male boxing are often viewed very differently it's still an amazing achievement.
It's not just Koseki in the bout however and her challenger with be Britain's Thai based 42 year old Denise Castle (2-0). Castle, who is a Muay Thai legend, will be Britain's first ever challenger to an Atomweight title and could well become the quickest Brit to ever win a world title, beating the record of Paul Weir WBO Minimumweight title back in 1993 in his 6th professional bout. Again men and women boxing are very different in terms of depth but it's still a great achievement.
With Castle's advanced Muay Thai experience it's likely that Koseki has got a real challenger on her hands here. Koseki might be one of the roughest and toughest female fighters in history but we expect she'll be having a real battle on her hands here.
For those wondering, this bout has been added to a show that already had a female world title bout on it with Naoka Shibata (12-3, 3) defending her IBF female Light Flyweight title for the second titme. Shibata, like her compatriot Koseki, has a hard test on her hands as she takes on Ana Arrazola (20-9-2, 13). Arrazola is a multi-time world title challenger who has shared the ring, twice, with the exceptional Yesica Yolanda Bopp and will be expected to give Shibata a very hard fight.
(Picture, of Koseki, courtesy of boxingnews.jp)