A second-year high school student in Tokyo, a science-minded boy in the physics club.

Kenji Koiso

17 years old, a second-year student at Kuonji High School in Tokyo. A member of the physics club, he is a shy and introverted science-minded boy. He planned to work a part-time job maintaining the network with a friend during summer vacation, but by chance, he is invited by his admired senior, Natsuki Shinohara, to visit Ueda City in Nagano Prefecture. He is gifted at mathematics, but he regrets failing the Japanese national representative selection for the Math Olympiad. However, that talent eventually becomes the trump card for facing a global crisis.

A refreshing beauty in a white dress.

Natsuki Shinohara

18 years old, the eldest daughter of the Shinohara family. She is the great-granddaughter of Sakae Jinnouchi. An idol-like girl at school who belongs to the kendo club, she is Kenji's senior. She goes to Ueda City, Nagano Prefecture, to celebrate the birthday of her great-grandmother, Sakae, during summer vacation. However, to fulfill her promise to Sakae to "bring a groom next time I come," she asks Kenji Koiso to take on the part-time job of being her "fiancé." She is a refreshing beauty in a white dress, but she also has a bit of a spacey side.

A world champion of fighting network games.

Kazuma Ikezawa

13 years old, one of Sakae's great-grandchildren. He looks like a dark, shut-in otaku boy, but he is actually a world champion of fighting network games and a master who controls "King Kazma, the King of Fighting" in the digital world. He is a super player with global corporations as sponsors. He is confident in his own abilities, and that attitude led to him being bullied in the past. He continues to train under the guidance of his "Master" to master fighting games.

The 16th head of the Jinnouchi family, which has continued for over several hundred years since the Sengoku period.

Sakae Jinnouchi

The 16th head of the Jinnouchi family, which has continued for over several hundred years since the Sengoku period. She is the head of a large family spanning four generations, including great-grandchildren. Celebrating her 90th birthday, many relatives gather from all over for the celebration. She has knowledge of ancient martial arts and is an elderly woman full of vitality that belies her age. Inheriting the spirit of her ancestors who served their local community during the Sengoku period, she has a wide network of contacts in the political and business worlds. She accepts Kenji, the suddenly appearing "fiancé," and leads the clan to face the global crisis.

Mansuke Jinnouchi

70 years old, the second son of Sakae Jinnouchi. He runs a fishery business at Niigata Fishing Port. He is an active fisherman who takes his own boat out to fish, and a physical powerhouse with master-level skills in Shorinji Kempo. He is the "Master" who taught Shorinji Kempo to his grandson Kazuma Ikezawa via OZ.

A wanderer, but the owner of a genius-level sharp mind.

Wabisuke Jinnouchi

41 years old, the illegitimate child of the great-grandfather who was the head of the Jinnouchi family. He ran off with the family assets and was missing for ten years, but suddenly returned on Grandma Sakae's 90th birthday. Apparently, he was immersed in artificial intelligence research in America during that time. In fact, that is the root cause of the major incident, and it seems to be related to "Love Machine"... He is a wanderer, but the owner of a genius-level sharp mind. He is also Natsuki's first love.

Takashi Sakuma

17 years old, Kenji's classmate and fellow member of the physics club at Kuonji High School. The physics club is commonly called the "PC Club," and their part-time job is OZ maintenance performed in the club room.