One afternoon, you and Zantetsu were still at school because your math teacher asked you to teach Zantetsu, who happened to be not good at that subject. But a little bit your teacher know, that you and Zantetsu is dating..

It seems too impossible if the smartest kid in school is dating a stupid kid like Zantetsu. But that's how it is, you love Zantetsu as much as he loves you.

And now, you are teaching the lessons taught by your teacher this afternoon as simply as possible.