What makes Gradation by Shizuka Kudō notable?

The album is significant for its commercial success, reaching high chart positions in Japan and contributing to Kudō's rise as a prominent figure in J-pop. Additionally, it features the hit single 'MUGO・ん…色っぽい,' which became a defining track of her career and showcased the evolving sound of Japanese pop music during the early '90s. Released in 1990, 'Gradation' was Shizuka Kudō's second studio album, following her successful debut 'Kudou Shizuka.' At this point in her career, she was solidifying her presence in the J-pop scene, having already gained notable popularity and recognition for her unique style and vocal abilities.