Many Japanese people on social media said the trademarked brand, Kimono Intimates - a play on her name - disrespected traditional clothing.
The reality-star-turned-designer, however, told the New York Times, it was a "nod to the beauty and detail" that goes into a kimono.
The loose long-sleeved robe dates back to 15th Century Japan.
She added: "I understand and have deep respect for the significance of the kimono in Japanese culture.
"My solutionwear brand is built with inclusivity and diversity at its core and I'm incredibly proud of what's to come."
The 38-year-old said she had no plans to change the name of the garment. Earlier this week she said the label "celebrates and enhances the shape and curves of women".
According to the Victoria & Albert museum, the term "kimono" was first used in the mid-19th Century and means "the thing worn" - but as an outfit, it dates back even further.
"We wear kimonos to celebrate health, growth of children, engagements, marriages, graduations, at funerals. It's celebratory wear and passed on in families through the generations," one Japanese woman, Yuka Ohishi, told the BBC.
"[This] shapewear doesn't even resemble a kimono - she just chose a word that has Kim in it - there's no respect to what the garment actually means in our culture."