Nande Koko ni Sensei ga!?

Originally a one-shot series titled "Golden Times."
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)