"I" (Boku) love math. Just after the high school entrance ceremony, "I" meet a beautiful girl: Milka. Milka is a mathematical genius. She gives me many maths problems, she shows me many elegant solutions. Milka and I spend a long time by discussing maths in the school library.<br /><br />One year later, I meet another mathematical girl: Tetra. Tetra is one year younger than me, and asks me to teach her mathematics. While I teach her, she begins to understand mathematics and gradually to love its elegance.<br /><br />In this second volume (series), we talk about Pythagoras' Theorem, Elementary Number Theory, Group, Ring, Field, and Fermat's Last Theorem.