Just after the high school entrance ceremony, "I" meet a beautiful girl: Milka. Milka is a mathematical genius. She gives me many math problems, she shows me many elegant solutions. Milka and I spend a long time by discussing math 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 math. While I teach her, she begins to understand math and to love its elegance gradually.<br /><br />In the first volume (series), we talk about Fibonacci Numbers, Harmonic Numbers, Finite and Infinite Sums, Factorization, The Bazel Problem, Partitions of the Integer, and Generating Functions.