northeastern unlucky direction; demon's gate
In traditional onmyōdō cosmology, the northeast direction is considered unlucky and is called the demon's gate. Figuratively, it can refer to a person or thing that brings bad luck or should be avoided.
Many people avoid the northeastern direction when building a house.
Used for a personal weakness, a subject one is bad at, or a situation one finds difficult to handle. Often appears in phrases like 鬼門だ or 鬼門になる.
Math has always been my weak point.
That boss is a person to be avoided for him.
Speaking in public seems to be his Achilles' heel.
unlucky quarter (southwest)
From the on'yomi reading of 鬼 (demon) and 門 (gate), originally referring to the northeast direction in onmyōdō, which was considered the direction from which demons enter. The figurative meanings developed from this unlucky association.