Angelegna was conceived by the DOD2 development team for their personal amusement. Visuals were made simply to be a bonus for DOD2's materials book, a move which surprised Akira Yasui in his commentary for the gag. The chances of the concept being put into actual development are 0.01%.
It is pitched as a dating sim which places the DOD2 characters at Seal Academy, a contemporary school setting. The description jokingly notes that there are eleven possible romantic endings, meaning that every character would have had a personal route with Nowe.
Dengeki Online conducted a follow up interview series to their character popularity poll with series's producer Takamasa Shiba and series's character designer Kimihiko Fujisaka. The Dengeki interviewer asked if there were any real plans to make Angelegna into a game, noting that it was a popular fan request in their questionnaire. While both Shiba and Fujisaka were amused by the nostalgic reference, Shiba remarked that Angelegna was quickly scrambled together in the waiting time before the game's public sales date and not meant to be taken seriously; actual production of the project would be difficult now since the timing for it would've been best shortly after DOD 2. He would personally enjoy the birth of a DOD school spin-off, though developing it would be another matter altogether. Fujisaka commented that he didn't spend too much time on the Angelegna designs as a result. They praised Manah, Legna, and Angel's designs during the interview.
The main cast have slightly altered character descriptions.
- Nowe - Protagonist and player character. New student at Seal Academy. Doesn't excel at his studies but he is an ace for the athletics club, so much so that he is heralded as "Messiah." When he is aroused, he activates the explosive yet mysterious Dragon Eye power.
- Eris - Class president and Nowe's childhood friend. She is an upright and decisive person who is especially strict to Nowe. Known as the "Disciplinary Goddess" and isn't very popular.
- Manah - Mysterious transfer student and school idol hailed as "Saint" by male students. Possesses a calm maturity that isn't common with teenagers. For some reason, she wears the same bracelet as Nowe.
- Urick - A senior student who has never graduated and continues to enroll. Strong fighter who goes by the nickname "Death". Sometimes walks around wearing a strange mask and has a personal preference for wearing baggy pants.
- Caim - Silent math teacher who is known for his radical teaching method of only writing on the blackboard to communicate to his students. Rumored to have been married to Angel.
- Verdelet - Founder and principal of the school. Deep believer of the school's policies. Completely unaware that Gismor intends to overthrow him. Parents often criticize his outlandish head tattoos.
- Zhangpo - Selfish school administrator who doesn't have a lot of friends. Walks around with a broom to clean up after others. He is secretly developing Ifrit, the school's mega powered incinerator.
- Hanch - Pale school nurse who is hated by men. She once won the "Smile Like Sunshine Contest" but she has had awful luck finding a male lover.
- Yaha - Radiant art teacher who has fans from both genders of the school. Urick doesn't take well to him for some reason. Recent hobby is clay art.
- Gismor - Power-hungry vice principal who aspires to take Verdelet's position for himself. Oddly popular with students whom commonly refer to him as "His Excellency."
- Legna - Mysteriously appears before Nowe before the school culture festival. Mysterious man in a black coat with puppet. The puppet has its own personality, and the man says it contains the Memory of Blood within it.
- Angel - Mysteriously appears before Nowe before the school culture festival. Woman agent wearing a red mask. She climbs on the rooftops of nearby buildings to observe the school. Looks young but speaks with an archaic tongue. Apparently frequents the convenience store but has trouble using microwaves. She often asks Caim to use them for her.