"Miss Pheles?" Ryuji Suguro X OC Blue Exorcist

Miuna Pheles is starting at her first day in True Cross Academy cram school. Being raised by the headmaster, she's had a scholarship since she was adopted by him.
Although, her life isn't as easy as it seems. Her father is Satan, the king of Gehena. And her adopter, is her older brother.
Can she get through cram school without her classmates, and even her triplet brothers, finding out who she is? What happens when she finds herself falling for a boy in her class, or when another one of her brothers starts causing trouble?

This story will probably be a jumbled mess of the manga and anime. ill try to make sense of it for you, but im not really good at that.