She is Hajime Nagumo's mother.
Sumire is a woman in her thirties with a slender build, and medium-long black hair.
Sumire is a loving mother and wife that possesses many otaku habits.
She is very cunning and can be deceptive to the point that she tricks her own family into involuntarily providing her with ideas for new stories through their antics that she sets up.
When Sumire was in high school, she disguised herself as a shrine maiden during the New Year holidays. She also saw a collage student named Shuu (who had also disguised himself as a shrine priest on him own) slacking off on his own before he was reprimanded by the real shrine priests. Sumire was soon caught as well by a real shrine worker. The two of them initially thought they would be in trouble for posing as shrine workers, but their disguises were so perfect that the real priests thought that they were actual employees and were disciplining them due to thinking that they were slacking off on their duties. Shuu then blatantly claimed that he wasn't a shrine employee and lied that the shrine clothes was his regular attire. It was then that Sumire fell in love with Shuu, which prompted the two of them to start dating, and eventually marry each other. At some point, they had their first and only child Hajime. In addition, Sumire would eventually become a famous shoujo mangaka, to which Hajime occasionally helped her with her work.
When Hajime and his entire class disappeared without a trace during his second year of high school, Sumire, Shuu, as well as the parents of the other students, did everything they could to find them, but to no avail. Eventually, many of the parents gave up searching for them, but Sumire and Shuu kept on searching for their son without rest (much to the concern of their friends), and used whatever means that could (even joining online web boards that talked about other missing children that disappeared under mysterious circumstances). One year after he disappeared, Hajime suddenly returned home in the middle of the night. After a very emotional reunion with his parents, Hajime spent the entire night telling them about his adventures in another world. Afterwords, Hajime wondered if his parents would still love him after revealing that he had killed other people during his adventure, but Sumire and Shuu assured him that they would always love him. Hajime then followed up by having his wives Yue, Shea, Tio, and Remia, as well as Remia's daughter Myu, spontaneously appear in front of them, much to his parents' shock. After learning the nature of the relationship between them and Hajime, his parents became hysterical, but soon calmed down when Myu expressed her concerns that they did not like her based on how they were acting, to which they suddenly became more courteous and expressed their joy at her and the others becoming important people in their son's life, and welcomed them to their family. They spent the rest of the night seeing recordings of Hajime's otherworldly adventures.
- Shuu Nagumo - Sumire's husband. The two of them love each other very much.
- Hajime Nagumo - Sumire's only son. She loves Hajime and becomes deeply distraught after he disappeared. Both Sumire and Shuu imprint Hajime with their otaku habits (as well as even making a list for him called "The Seven Most Important Things for an Otherworld Summoning").
- Liliana S. B. Heiligh - After moving to Earth, Liliana becomes Sumire's protégé as a shoujo mangaka.
- Sumarie's surname "Nagumo" means "south cloud" (南雲).
- She is capable of using Hajime's artifacts even better than Hajime himself.
- Web Novel - Chapter 247
- Light Novel Volume 10