Datong's dream before that school day fight with the bullies..
In a psychward.. some head pokes up his windows.. Datong now alert!.. two patients with him! One guy walks in!.. gets Datong to come with him outside in where the dream location turned into some door resembling a backdoor of a house! Trying to seem like he was showing him something important like a friend!.. Datong knows his obvious plan.. he thinks he's gonna surprise one punch Datong! Their plot!.. Datong lets him to prove a point! I'm INVINCIBLE! ..with their strongest absolute punch knocks a tooth in his mouth and with the quick choice has has to make to swallow or spit and swallows thinking it will come out . Datong feels no pain whatsoever!.. And beats the shit out of him so easy! As the enemy is down and in true pain..and looks at Datong thinking, "Why is he so strong..why.".. Datong looking down on him.. and starts to talk.
Datong: Ha I knew your plan! I let you hit me! What?! Did you think I trusted you?! Do you think I'm that stupid?! By the the way! I'm rearranging your face! Have an embarrassing funeral loser! That's for my tooth! Merry Christmas!