Main Character:
Takayama Kaito / Lucifer
Heroines:
Koneko / Shirone (Highschool DXD)
Shiina Mashiro (Sakurasou no Pet na Kanojo)
Relevant Secondary Characters:
(These may become future heroines, recurring characters, or important figures within the development of the lore.)
Makima (Chainsaw Man): Based on the character of the same name in terms of appearance and personality, although the story of Chainsaw Man does not exist in this fic. She can be considered this world's version. She is the receptionist of the guild (in the protagonist's city branch) and a rank 4 demon.
Sonya (Original): A dark elf, former member of the royal guard of the elven kingdom in the Dark Forest. Level 4 mage in shadow arts and mentor to the protagonist in this discipline.
Sylver(Original): A two-headed Cerberus, leader of the Hellhounds under the protagonist's command. At first, he was accompanied by his pack of silver wolves, but they evolved thanks to the protagonist. He also gained the ability to summon more, so his pack continues to expand constantly.
Lorim(Original): De facto leader of the beastmen under the protagonist's orders. Originally the chief of a kobold village subjugated by Kaito. After joining, they received a tower where, by overcoming trials, they can evolve into beastmen. Although the population has grown exponentially and Lorim is no longer the chief of the original village, most still recognize him as a guide and trusted figure.
Korran(Original): Captain of the beastmen combat force. He was the only kobold who dared to challenge the protagonist upon his arrival, thus earning his recognition. He currently leads the warriors of his race, although not all kobolds and beastmen choose that path.
Ben(Original): First human summoned by the protagonist and later transformed into a demon. He is the de facto leader of the demons under his command. Although each of the 72 demon houses has its own leader, Ben serves as the main representative before Kaito.
Nyssara(Original): Lady of the city of Nareth, the first elven city conquered by the protagonist. Expert in wind spells. Younger sister of Sonya.
Ryselle(Original): Lady of the city of Veldris, the second elven city under the protagonist's domain. Specialist in fire spells. Younger sister of Sonya.
Colette(Original): Lady of the city of Velanyr, the third elven city conquered by the protagonist.
Viktor Asano(Original): Leader of the guild branch in the protagonist's city.
Hikaru Saito(Original): The protagonist's best male friend in the real world.
Aoyama Nanami (Sakurasou no Pet na Kanojo): Close friend of the protagonist.
Kirigaya Kazuto / Kirito (Sword Art Online): Ally and acquaintance of the protagonist. Possesses an ability that allows him to create sword techniques, almost at the level of real skills, which others can also learn.
Takayama Sora(Original): The protagonist's younger sister.
Takayama Sayuri(Original): The protagonist's mother.
Frey(Original): Under the protagonist's command. Member of the Phoenix house, occupation: tailor.
These are the most relevant characters so far. Some lack additional information because it has not yet been revealed in the story; this list will be updated as needed.