In Professor Yasuhito Sato's seminar, students created a booklet as their graduation project titled "A Message from the Aging Economics Seminar: What You Need to Know About the Future of Population Decline and Aging." This booklet represents the culmination of two years of learning in the seminar about intergenerational inequality, low birth rates and an aging population, and population decline. We realized that the problems of an aging society have many impacts on our lives, and we created this booklet with the hope that our peers will learn about population decline and aging. It provides an easy-to-understand explanation of population decline and aging from a student's perspective.