Depression: (
Story/Location) Titles that contain characters who suffer from depression would fall into this category if this is of significant importance for the storyline.
Tragedy: (
Genre) Animes of this type have tragic events as an important part of the story, and usually will show how the characters are dealing with the consequences of that tragedy (more or less successfully). This doesn't necessarily mean the story cannot have a happy ending as the tragedy might occur during the first episodes of even before story begins; as such this category information need not be a spoiler (unless the tragedy were to be a surprise for the audience in a mystery-style show).
Parody: (
Genre) This would be a title which closely imitates another title, genre, culture, etc. for comic effect or in ridicule.
Soul Mates: (
Story/Location) Mentioned only in terms of extreme romantic entanglements, there are situations in which two people (or souls) are destined (or pre-destined) to have a strong emotional attraction or involvement.