From the contents: From the spread of infectious diseases to false positives/negatives in testing, the Black Lives Matter movement, DNA analysis in criminal trials, and even choosing a marriage partner. Mathematics is behind the scenes of major events. Mathematics permeates your life, holding the power of life and death. Whether you live or die, it's up to mathematics. In fact, there are countless examples of people who have lost their lives, lost their fortunes, or been falsely accused because they didn't know or misused mathematics. Conversely, just by being able to use a little bit of simple math, you can see through the lies of the media and politicians, avoid being caught in scams, and correctly understand the results of your health checkups. Furthermore, it might even help you choose your ideal marriage partner... A brilliant mathematical writer, who is also a mathematical biologist, explains the relationship between your life and mathematics while introducing numerous examples. Please read the profile section.