Why the Hell Are You Here, Teacher?!

Teacher..wh-what are you doing here? You're not allowed here, and moreover.. Well, yes, I can see that you're having a problem, but you really should.. Wait, why are your clothes coming off? Wh-what's happening??? Wait a second.. Why the Hell Are You Here, Teacher?! (Source: BookWalker) Notes: - Originally a one-shot series titled "Golden Times." - Includes 11 extra chapters.