gloom (expression)
When a character is visibly depressed because they are disappointed, often the result of this is from a situation that ended quite comical, at least from reader's point of view.
Besides the facial expression, other indications of comical gloom include dark straight lines, a dark aura, or hitodama around the character.
If the character is depressed due to overwhelming sadness or genuine distress, use despair or traumatized instead.