This is a study of LY3484356 in Chinese participants with advanced breast cancer. Participants must have breast cancer that is estrogen receptor positive (ER+), HER2 negative (HER2-). The purpose of this study is to measure how much LY3484356 gets into the bloodstream and how long it takes the body to remove it. The safety and effectiveness of LY3484356 will also be studied. Participation could last up to 28 months.