Well, it's just about a big desire - I've never studied how to sew, but I tried very hard to make it look close to one in anime. I really wanted to make it %) And for the patterns - I didn't use them in this jacket, it is all about simple measures
I'll try to explain somehow x) Well, the measures for the collar itself and for the collar of jacket are the same. All, that you're really need here - make your collar of two details (or two layers), which are, of course, the same. You can correct the width or the length of the collar as you wish. The collar is fixed in the area of the seam (there two parts of the jacket are sewed) and also by the buttons (you can see them on this photo (there are also two buttons on the back side of the jacket).