Most people in my age or older learn calligraphy after school.
It is not because parents want their kids to learn the chinese letters.
People believes,
"Writing shows your whole personality"
You can see some of your personality in pencils too. But if you use brushes, people who learned calligraphy deeply see a lot of things from your writings.
Calligraphy lesson includes many things.
Create concentration
Keep proper posture (way to sit, positions of elbow and hands, how to hold the brush)
Enjoy unique effect of "Ink and brush combination"
Learn Japanese as art
more.....
Calligraphy does not train only writing skill but also teaches real cultural things.
