sentences:  3, Wang Ya Se, also called Ya Se Wang (Calvin Chen), and KO.4, Ding Xiao Yu (Aaron Yan) soon join the class and out of some fortuitous events, their lives become tied together and they become best buddies.Another student, Lei Ke Si (Danson Tang), who had been gone for a whole semester, rejoins the class.Although Lei Ke Si seems like a weak kid with only good intentions, Ya Se suspects Lei Ke Si is KO.2 because legends say that KO.1 and KO.2 are capable of concealing their true identities.