Hiromi san , Recently i read this book Written by Mr. Manoj Vasudevan
"How To Become The World Champion of Public Speaking:
Invaluable Insights from Losing, Winning and Coaching"
Author was an introvert in his early times and he explained the process on
how he managed to over come it . Process is just attending Toastmaster meeting regularly and take a little more initiative to Practice Public Speaking (Practice , Feedback & learning ..Repeat.....)
This is the only way we can learn more of public speaking..Hope you know this already
Thanks for your Question