Koshi Nagumo (南雲 孝士, Nagumo Kōshi) is the main protagonist of Megami-ryo no Ryobo-kun. He is a junior high school student who gets a job at the dormitory after his house burned out and he is abandoned by his family.
Koshi is a cute young boy with short dark-brown hair and light-brown eyes.
Koshi is a quite responsible and mature boy for his age who tends to hide his true feelings after being abandoned by his father. Koshi is easily flustered by the girls behavior and raw sex appeal, but has great willpower to resist seduction. Nonetheless, He takes his responsibilities as their dorm mother seriously as, even though the girls were older than him, he didn't hesitate to scold them for their bad behavior. He even tries to warn them to be more aware of how they act and dress as he is still a boy and has desires. As he bonds with the girls more, he becomes more aware of them as woman, but he is hesitant to act on these feelings.
Koshi has pride as a male, as he was embarrassed from being forced to cross dress and hoped it would never be revealed, only to be horrified when it was. He was also angry with himself for not being able to swim and save Sutea Kouroya from drowning and had to ask for help instead. Koshi also dislikes acting his age, feeling very embarrassed when he does, as he feels he needs to act mature as a dorm mother and not a child.
Being abandoned by his Father after losing his house clearly scarred Koshi emotionally. During his "duel" with Frey, he broke down mentally and collapsed in anguish after remembering it. He also revealed he refuses to try and see the girls of the goddess dorm as members of the opposite sex for fear of losing his job, home, and surrogate family. In the anime he had a nightmare during his fever about his home burning down. During this nightmare, he was notably paralyzed with fear and breathing heavily.
Perhaps, Koshi’s greatest quality is his empathy. He refused to become the dorm mother at first because Atena would have left and he knew how painful being homeless is. He also counsels the others about their insecurity’s and gives them confidence. He will also get angry for their sake against others who undermine their hard work or make them feel bad such as boys who hit on them.
On his birthday, Koshi's house burns down and having no money, his father decides to abandon and leave. Roaming the streets, he falls exhausted from hunger. Mineru Wachi finds him and takes him to her dorm, where she gives him food. There he meets the other members in the dorm. Learning about Koshi's situation, Mineru proposes he lives there and works as dorm mother. Only Atena Saotome is against it as she can't handle being close to men. Koshi decides to turn the offer down as he doesn't want to make Atena to not feel at ease at her home. Seeing how considerate he is, Atena decides to accept him and allows him to be the dorm mother.
Koshi then starts doing daily chores, but while doing so, he often runs into the troubling members. Mineru often works with poisonous experiments and walks naked. Frey likes to cosplay and forces Koshi to be her model. Kiriya Sensho a martial artist who gets excited while reading shoujo manga and relief stress by punching the walls. And Serene Hozumi who uses him as a servant and kisses him while he sleeps at night.
Due to her Androphobia, Atena was against him staying at the goddess dorm. Due to his considerate personality, Koshi bore no ill will from this and left rather than make her feel uncomfortable in her own home. Feeling guilty from her selfishness, she saved him from freezing to death outside and accepted him as a dorm mother. This incident led to Koshi being the only male she is somewhat comfortable with and can touch. While Koshi saved her from a panic attack in public, he called her sister which awakened a hidden perverted brocon feeling in her. Since then, she has obviously acquired feelings for him and desires him to address her as sister. Koshi currently sees her as a big sister but is frequently overwhelmed by her and the other dorm girls sex appeal and weird behaviors. Later, Koshi began to subconsciously develop feelings for her as he was jealous at the thought of her giving chocolates to another man on Valentine’s Day.
Mineru found Koshi on the streets malnourished and dying. Taking pity on him, she took him to the dorm and fed him, and also gave him a job and home, earning his gratitude and respect. She was also considerate enough to enroll him to school without him asking. However, he is frequently overwhelmed by her sex appeal and chemical hazards from her experiments. Koshi understands her very well as he instantly understood she was scared of ghosts and put up a confident front. Mineru once had a brief and tense romantic moment with Koshi after he supported her fear of ghosts. Mineru’s true feelings after this are unclear as she does not know if this moment was brought by lust or simple fear.
Koshi hates his father for his irresponsible and selfish behavior. When he lost his home, his father abandoned him and Koshi never wanted to find him again.
Koshi often treats Kiriya as a woman and regards her as tough but cute. When Kiriya confides in him her love for romance novels and how she feels pressured by being a model student to the school, Koshi always understands her and offers support. This led to her developing feelings for him, though she occasionally gets carried away and wrestles with him and hurts him. Koshi knows she doesn’t hurt him on purpose and always forgives her, making her more embarrassed around him. They once even accidentally got into a sex position after Koshi fell on her in the bathroom (unknown if the deed happened). This incident was so embarrassing for them they never brought it up again and were terrified when Atena Saotome and Sutea Kouroya saw them. Kiriya once even attempted to kiss Koshi during Christmas when he gave her a sincere present.
Frey frequently uses Koshi as a cosplay model and playmate, ignoring his discomfort for it. Despite this, she has shown a deep understanding of the pressure and sadness Koshi keeps hidden as not to burden the girls in the dorm. She manages to relieve him of some of this stress by cosplaying as a warrior and sparing with him. He reveals to her only that he is scared of being with them romantically for fear of ruining the good relationship they share now. She has earned his trust and confidence after this and proves to be the support for him like how he is for the other girls in the dorm.
Ever since they were kids, Koshi has helped Sutea with her extreme adversity to heat and body touch. Since he was the only one at school that understood her plight and keeps her cool with ice packs and water, she developed feelings for him which are obvious to everyone but him. However, her violent tsundere side makes it impossible for her to convey these feelings. She was angered and sad when Koshi didn’t call her when he lost his home (due to not owning a phone) and tried to protect him from the Goddess dorm. She once hit his testicles so hard it was implied to have destroyed one and knocked him out. She always feels remorse for hurting him and often tried to protect him, only to comedicly fail and make it worse.
Serene treats Koshi like a servant, acts like an alien and kisses him in his sleep. These traits make him feel the more uneasy than with any girl in his life when he is around her. She appears to have a growing interest in him as he is still thoughtful of her enough to fix her favorite clothes and ease her discomfort of being in public.
- The name Koshi means "filial piety, obedience" (孝) (ko) and "samurai, warrior, gentleman" (士) (shi).
- Koshi's surname Nagumo means "south" (南) (na) and "cloud" (雲) (kumo/gumo).
- Koshi's first kiss was taken by Serene Hozumi.
- Koshi doesn't know how to swim, likely due to his Father being neglectful and never teaching him.
- Due to a aphrodisiac pheromone accidentally released by Mineru Wachi in public, Koshi was almost molested and raped by several woman.