Sorry for the late reply. Was tired but feel better now. :)
Kou nodded. He looked at the library, at book-filled shelves and student-occupied tables, and wondered how to explain how important mathematics was. Shiori was a nice girl, perhaps a little dim, but nice. She was clever in her own way. She'd understand maths. It was in the world around them, he thought - and that gave him an idea.
He pointed at the shelves on their right. "Somebody designed that to exact measurements," he said, and then pointed at the books. "Numbers of pages." Lighting. "How long the bulb lasts."
He looked at Shiori then. "Your shades of pencils. Graded. If you need help... I suppose I have the time."