Helg, from which archives did you dig this pic out of? It's actually quite comical because of the way it is staged.
Initially, most (probably 99.99%) viewers immediate reaction would be "holy crap, that guy is about to be chopped up into a zillion pieces of sushi!"
It's clear that this image is a western distortion of eastern reality. For starters, unless a married Japanese woman (unmarried couples don't cohabitate and that man doesn't look old enough to be her father) is absolutely positive that her husband is cheating on her, she would virtually never commit adultery, particularly in her own home. They have special hotels for that kind of behavior.
Next, there is the bed. Sorry guys, but most Japanese sleep on a futon spread out on the floor. Then we have the "hardcore samurai" wearing both a tradional gi under his jacket and hachimaki on his head. Only children wear their martial arts garb cycling to and from the dojo and nobody wears a hi no maru headband except on rare festivals.
Then we have the geta sandles on the wooden floor, which are strickly forbidden to be worn indoors.
Finally, the Chinese Kanji idiom written on the scroll above the bed. It's not even Japanese.
Helg, to answer your question, the meaning is abstract and a very rough translation would be something like: "life is complex, however scripture should be simple."
In the one in a billion instances where something like this could occur, the man entering the room might end up using the tantou dagger displayed on the wall, but most likely not on the pathetically wimpy English teacher you see proposing a toast.
Sorry to go into such depth, it's just that this pic is so far fetched that I had to comment.