Amada began practicing boxing as a teenager while attending Maebashi Ikuei High School, and won the national junior championship prior to graduation.

Eschewing kicks and utilizing a boxing-based style, Amada achieved a 5-0 winning streak en route to reaching the finals of his first tournament – the K-1 Spirits '99.

Despite this show of toughness, Amada – who had by then broadened his repertoire to include low kicks – peppered the American for three rounds while staying out of range of Esch's punches, leading to a unanimous decision victory.

[4] For the remainder of his career, Amada competed for a variety of organizations but found the most success in HEAT, a fledgling promotion which held all its matches in an octagonal cage.

He entered a tournament to crown the company's first heavyweight kickboxing champion, and eventually emerged victorious with a KO win over Makoto Uehara at HEAT 10 on July 18, 2009.

Despite being 40 years old at the time – over a decade older than his opponent, Kengo Shimizu – Amada surprised the audience by being the more aggressive fighter, pushing in close with his signature boxing offense.

[5] Amada fought his last match to date on September 18, 2016, at the New Japan Kickboxing Association's Titans Neo 20 event, achieving a unanimous decision victory over Mauro Herrera.