Both cheesy stories involving vampires, with similar feeling to them. In both dramas vampire(s) provide help in order to stop crimes, and seem to see humans not just as food source.
It focuses on a naive, loudmouthed teenager named Rion, who investigates a host club full of vampires when she suspects they must be related to the disappearance of a lot of people in the neighborhood, including her best friend. In the process she begins to befriend them, especially the leader Suou, with whom she develops a romantic relationship. Ultimately, she figures out the vampires are not the cause of the disappearances, but her adventures with the vampires are only beginning
A story about a temporary-staff worker who finds refuge in the fantasy world of a comic, Rose of Versailles. Katsuko's mediocre days is put to an end when the son of her company president arrives at her office and lays out unreasonable a cost-cutting policy which upsets Katsuko. Her inner ear hears the voice of Oscar, the main character of "Rose of Versailles" who stands up for the people, and decides to take action against him to save her helpless colleagues
They are both about traumatized young boys finding brothers to protect and get them through. In RH+, the brothers are adopted and vampires; in Fallen Angel, they are actual kin. But still, the bromance feeling is the same. Both shows are mainly centered around the boys and have supernatural/psychological thriller themes.