As well as having Korean teachers and native English language speaking teachers, my workplace employs a handful of extra local 'teachers'. They don't do any teaching but spend the duration of classes in the corridors marking papers or preparing some materials for the rest of us and of course completing lists of all the students who have to. These are Jaeshi (재시) teachers. Jaeshi loosely means retest. Where I work, students who don't do their homework, perform very badly repeatedly in class or have poor class test scores get jaeshi. They stay behind after their classes have finished for around an hour or so.
In over two years working at my academy, in largely the same rooms, I have seen lots and lots of Jaeshi teachers. Some I have become friendly with and some who just don't like talking with non-Korean speakers. They all seem to be university students trying to make some money in a part-time job and who from time to time are studying English, but usually not. I talk to them a bit and joke around, trying to make my work as fun as possible because it's repetitive. There is a language barrier but communicating seems to work OK. The rooms I teach in are side by side and right next to the jaeshi teachers desks so I can see them working and they can see me (not) working etc etc. There's no room for me to hide. Or them.
This week on the way to a class a few of the jaeshi teachers were joking that I never buy them a coffee and I always have a cup in class, calling me a "rich guy" etc, etc. After the joking around I said I'd by them some coffee. All this week I've had "bad guy" and "liar" amongst others because I didn't 'pay up'. After another verbal battering today, I gave them ₩10,000, roughly £5 to buy them some drinks from the coffee shop below our school and asked them to get me a drink too. They were very surprised when I actually said I would buy them a coffee. They somehow managed to get my drink and enough coffee to be split between five of them, which I found very impressive. Afterwards they treated me like a prince with some silly and over-the-top compliments (like I'd fed a starving child) and gave me this piece of paper, below. I hope they liked their coffee, the shop I go to needs the business.