Forgetting to unregister at my ward office

So here is the situation. I have been living in Japan for 2 years now on a ryugakusei visa. I graduated from the school (language school) i was attending about a week ago and have been accepted into a university. Since my university does not officially start till the end of march, I have to go back to my home country for 3 months and apply for a entirely new visa. It is annoying but accept that fact.

Here is the problem. I found a cheap plane ticket back to my country but I leave from Tokyo. I live in Kansai and already have traveled to Tokyo. I thought i had tied up my loose ends but stupidly forgot to notify my ward office and get the 転出届(tenshutsu todoke), so they know i am leaving the country. My question is, is it possible for me to notify my ward office from Tokyo so I do not have to waste my money and time traveling back to Kansai? I leave Japan in 4 days. Can I do this this process through the mail?

Any insight would be greatly appreciated!

The procedures at municipality offices, including move-in/out notifications, are not uniform nationwide; every office does them its own way. So it's impossible to answer this question without knowing which office it is. And why do you not ask them that question yourself anyway?