The Devil Within is about a teenage girl who dislikes grown men and has feelings for her younger-looking neighbour, Tenshi.

The manga was published in Japan by Shinshokan, running in Wings magazine between September 26, 2002, and October 26, 2004.

Now that Rion has grown into a pretty young girl, she only has eyes for little boys and avoids “devils” at all costs.

The manga starts as her father – “the big devil” – is coming home from being out of town.

Rion goes to buy groceries for dinner and on her way home she is attacked by a scruffy-looking vagrant who is demanding food.

Luckily, a handsome man stops the attack, but Rion thinks it’s a ruse perpetrated by the two of them to get to her.

When Rion makes it to her room, the scruffy vagrant, the handsome do-gooder, and the man from the elevator are all there waiting for her!

After her adopted father arranged her to pick three boys as her fiancé, Rion slowly begins to open up to them.

After Tenshi lashed out at her, thinking that he was stuck in his child form because of her, Rion went to confront her father.

Scared, Rion told Tenshi what happened and then went off to ask Somi, one of her fiancés, to sleep with her.

After trying to figure out how to cure them of the Devil and Angels' DNA, Rion concluded that the only way to achieve this was to have sex with one of them.

Rion hoped her fiancés would give up on her after learning this, but Somi, Fuuya, and Koki were even more determined to win her over, much to her and Tenshi's dismay.

Before the story took place, Koki wanted for money, so he made a blood contract his adopted father, an Angel.

After Rion witnesses Somi's sadistic other side, he comforts her and tells her about the Devil blood that runs through her.

After Rion's agreement with her father that he will change Tenshi back to his true form if she sleeps with one of her fiancés, Koki was not the one she picked, because she was scared of his aggressiveness.

Seeing how to keep them from shifting by having someone they love talk them back to normal, Koki, along with his brothers, was more determined to win Rion's heart.

Fuuya tended to look like a cute girl when he cried to Rion, and was usually the one she felt most comfortable around.

But Fuuya knows the only way to be human is to take Rion's virginity, and the bad part is him and his brothers are slowly growing feelings for her.