I love math. Just after the high-school entrance ceremony, I meet a beautiful girl: Milka. Milka is a mathematical genius. She shows me many math and many elegant solutions. Milka and I spend a long time discussing math in the school library.... more>>

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 gradually to love its elegance.

The third series is about logic puzzles, Peano arithmetic, epsilon-delta, Cantor's diagonal argument, Hilbert's program and Gödel's Incompleteness Theorems. <<less

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While riding home on the bus one day, a girl sits down by Sai and lays her head on her shoulder while she sleeps. When... more>> she leaves she leaves behind her lip balm. Sai then becomes obsessed with returning the lip balm, taking the same bus every day. What will Sai do when she finally meets with the lip balm girl again? What are the feelings that underlie her obsession? <<less