Hello,
In my first visit of Japan I have one free day in Tokyo. Can you please suggest any popular attractions or sights, that are accessible for a single, non Japanese speaking person?
I am also interested in anime subculture and would like to visit Akihabara, however I am not deeply familiar with it, hence I am looking for a good place to go to there (as it is a big place and one day would not suffice to explore it fully).
I understand that this would be hard and I am thankful for any suggestions.

Akihabara is easy to get to. Depending where your staying that is, but, all you do is hop on the JR Line, and it'll take you right to Electric town (Akihabara), and then you just follow the signs.

Sounds easy, and it is. My first time in Japan I was there for 6 days on my own in Tokyo, and I had no problem finding it. The JR Line is basically a big loop. So, if you hop on the wrong JR train (Green), might take you longer (like 30 mins maybe) but you'll get there.

A full day, you can see lots using the JR line. Akihabara, and then take the JR line again to Shibuya. Go at night, it's pretty cool. Hell, you can do alot in a day.