Because he is afraid of Min Woojin leaving him without explaining everything like in the past. He is in love with him and was really hurt by that. You will see later on in the next coming chapters (Chp. 22-23).
Because the guy is still hurt that his so called "Good Friend" disappeared from him. He mentioned it himself, if the guy really loved him and cared about him he wouldn't have left him and stayed by his side. That's why he doesn't bother mentioning his real name, cause he still has a deep seeded pain in his chest, where his "best friend" someone he loved a lot and cared about just went up and left him without mentioning anything. Tae-Min took it as a betrayal, he thought that the other guy didn't care about him as much as he had.
well I know that but still... what a resentful guy... they where only child and whit hard circonstance. I m sure it's not like he could have done anything anyway...
well, we will see later I'm sure ╮(￣▽￣)╭
it's not about resentment... If Taemin was resentful he would hate Woojin... This about distrust... Taemin is afraid of beinig hurt again. What hurt hia was Woojin leaving him without saying goodgye if giving him any explainnation, sure Woojin can tell him I love you but usually actions means more than words... can you trust someone who saysI care about you but abandoned you before and never made an effort to keep in contact or appologise or something before, in years? Can Taemin trust someone who was aggressive and even hit him before ? sure Woojin thought he was Siwon but is that an excuse for hitting someone who was in trouble and who was a victim, just because his face or his new attittude was annoying or whatever ?
I don't understand why Teamin don't want to admit who he is... after all it's his friend and whit this he could finally have someone who he can freely talk to.... and NOWAY! his body is dead ┗( T﹏T )┛