Hi yoshimasa,
I think your engine with EN number should have the smaller flywheel.
Please have a look in the center:
may be there is an "extractor ring" (small ring srewed into the flywheel above the center fixing nut) already fitted in the flywheel.
When you have this ring, you have to unsrew the center nut, after some revolutions the center nut will touch the extractor ring and with further turns you will extract the flywheel from the cone.
If there is no ring inside the thread of the flywheel, you can also use an separte extractor.
I have both parts for my bikes.
My bikes have the bigger dia flywheel (235mm), outside thread is 38,2mm x 20G) on extractor.
I can not manage to send a photo on the forum, may be to many pixels?
If you want, you can send me a private email to send you photos.
Michael