What is UNIQLO sister brand in Japan?

Excuse me, I'm curious to know about UNIQLO's operations in Japan. Could you please enlighten me on the sister brand of UNIQLO that operates within the country? I'm particularly interested in understanding how this brand is positioned within the market and how it differs from UNIQLO, if at all. Additionally, I would appreciate any insights you might have on the brand's history, target audience, and any notable collaborations or achievements.