ルナルナアプリ is a free menstrual cycle management app that has been downloaded over 18 million times and celebrates its 20th anniversary. It provides essential information for women, including the next period and ovulation dates, optimal times for pregnancy, difficult times for conception, and recommendations for diet and daily health. Developed by MTI Ltd., the app offers a unique algorithm for predicting ovulation dates based on over 15 years of accumulated data. It also allows users to record and access their data during visits to gynecological clinics. With a user-friendly interface and a clear calendar display, ルナルナアプリ is a convenient and accessible tool for women to manage their menstrual cycle and overall well-being.