Excuse me , english is not my maternal language :P so i did not really understood the end ...

I think that the chapter 57.2 is the last of this manga ..

Basically I think it meant that no one would remember the existence of a 'Min Woojin' when he assumed the place of 'Min Siwoon', so Min Woojin is essentially dead to the public and Min Siwoon lives. I think they meant to highlight the fact that only Taemin really remembers who Woojin really is just like Woojin remembering Taemin.

I think it helps when you listen to K-pop. Because then you are kinda used to korean and learning the names is easy then.

Heheh. Kpop might have something to do with it but I think it's more of understanding the story and characters. Min and Han are their family names, so Min Woojin, Min Siwoon, Han Siwon, Han Jiwook, that's easy. And then obviously there's our Yoon Taemin which you can't forget. And Joohoon. But that's it. Don't remember any other names.
Now I feel sorry for the two sidekick best friends. ╮("￣▽￣)╭