Engaged to the Unidentified

Its chapters were collected in 16 tankōbon volumes. An anime television series adaptation by Doga Kobo aired between January and March 2014.

Kobeni Yonomori is a high school girl who lives with her mother and older sister Benio. Upon turning sixteen, Kobeni is shocked to learn that, due to an arrangement by her late grandfather, she is engaged to a boy named Hakuya Mitsumine who, along with his little sister Mashiro, come to live with Kobeni. As Kobeni spends time adjusting to this new family, she learns there is more to Hakuya and Mashiro than meets the eye. Soon, Kobeni's life becomes a bit more interesting between having a fiancé, a new sister-in-law, and a crazy sister.

Kobeni Yonomori (夜ノ森 小紅, Yonomori Kobeni) Voiced by: Haruka Terui A responsible sixteen-year-old who handles cooking and chores well. When she was younger, she fell down a cliff but was saved by Hakuya. The incident left her with a scar and little memory of the event, as she does not remember Hakuya when they meet again. Over time she recalls more of her memories of the incident, later learning she had received half of Hakuya's inhuman power, the side effect of which gives her a fever on occasion. In school she is noted for her cute face, large bust and (as Mashiro puts it) "child-bearing hips" (which she is conscious of). She is also very conscious of the unwanted attention she receives for being the student council president's younger sister. She begins to seriously date Hakuya later on in the series and go out on formal dates, although she is very nervous any time they do. Benio Yonomori (夜ノ森 紅緒, Yonomori Benio) Voiced by: Eriko Matsui Kobeni's older sister, who is the student council president at her school. She is both a siscon and a lolicon, and is incredibly doting on both Kobeni, who has gotten used to it, and Mashiro, who fears her greatly. She is quite popular at school, often putting on a more refined personality than at home. In school, she is called Benio-sama. She is protective of Kobeni as she feels somewhat responsible for what happened. Mashiro Mitsumine (三峰 真白, Mitsumine Mashiro) Voiced by: Yu-ri Yoshida Hakuya's younger sister, who was able to enroll in Kobeni's class despite being nine years old by using a hypnosis-like power to fit into the crowd. She often complains that she is not a child despite being no older than ten, but her true feelings regarding her likes and dislikes can be easily read by the others. She is quite fearful of Benio but is easily swayed by sweet things. She also has a fear of aliens and UMAs but becomes intrigued by the latter when she discovers toy models of them inside some chocolates. Hakuya Mitsumine (三峰 白夜, Mitsumine Hakuya) Voiced by: Wataru Hatano Kobeni's arranged fiancé and Mashiro's older brother. A quiet but kind-hearted boy who silently helps out Kobeni when he can, though is sometimes slow to catch onto things, and is not bothered at all with their arranged marriage, as he truly likes her. When they were younger he saved Kobeni's life after she fell down a cliff and blames himself for failing to prevent it. He injured his right eye in the accident, causing him to lose part of his vision. As a result, he grows his bangs long to cover up the scar. He has a hobby of constructing models of historical buildings from matchsticks, which are often ruined by Mashiro. It is later revealed that he is an Inugami, who gave half of his power to Kobeni to save her life. His usually expressionless face makes him a person hard to read, even to his family. Kobeni, however, seems to be an exception. He begins to seriously date Kobeni later on in the series and go on formal dates out. Mayura Momouchi (桃内 まゆら, Momouchi Mayura) Voiced by: Aimi Terakawa Kobeni's classmate and best friend, whose family runs a big chocolate factory. Nadeshiko Kashima (鹿島 撫子, Kashima Nadeshiko) Voiced by: Ayane Sakura The student council vice-president, who often has to keep Benio's urges in check. Konoha Suetsugi (末続 このは, Suetsugi Konoha) Voiced by: Saki Fujita The student council's secretary, she greatly admires and is fond of Benio just like everyone else at school (with a few exceptions: Mashiro, etc.) and is jealous towards Kobeni and Mashiro because they both live with her. She comes from the same species as Mashiro and Hakuya and seems keen on getting Hakuya to marry her because her mother told her to not miss the chance of claiming a male of their species due to their rarity. Niko Ōno (大野 仁子, Ōno Niko) Voiced by: Asuka Kakumoto Konoha's close friend and a member of the school's newspaper club, who is always on the lookout for a scoop to get herself promoted to the position of editor-in-chief. Akane Yonomori (夜ノ森 茜, Yonomori Akane) Voiced by: Yui Watanabe Kobeni and Benio's mother, who is often busy working. Shirayuki Mitsumine (三峰 白雪, Mitsumine Shirayuki) Voiced by: Yuri Komagata Mashiro and Hakuya's mother, who is petite and looks young for her age. She is easily distracted by sweet things and tends to blurt out important information casually. She is the one who casually lets slip that the Mitsumine clan is not human. Ui Komagamine (駒ヶ峰 初, Komagamine Ui) Mashiro and Hakuya's cousin, and Arata's younger sister. Ui has the ability to turn into a cat. And unlike Mashiro, Ui enjoys playing with Benio, even calling her "Benio-tan." Arata Komagamine (駒ヶ峰 新, Komagamine Arata) Mashiro and Hakuya's cousin, and Ui's older brother. Arata is a sixth grader. Konoha's mother has arranged an omiai (marriage meeting) between Arata and Konoha.

Written and illustrated by Cherry-Arai, Engaged to the Unidentified was published in Ichijinsha's four-panel manga magazine Manga 4-Koma Palette (formerly Manga 4-Koma Kings Palette) from April 22, 2009, to February 27, 2022, when the magazine ceased publication, and the manga was transferred to Monthly Comic Rex starting on April 27 of that same year. The series finished on March 27, 2024. Ichijinsha collected its chapters in 16 tankōbon volumes, released from July 22, 2010, to June 27, 2024. The fourth volume was released simultaneously with a limited edition on December 28, 2013, bundled with a DVD containing an animated music clip of the song Zentaiteki ni Sensation (ぜんたい的にセンセーション), performed by Haruka Terui, Eriko Matsui and Yuri Yoshida.

An anime television series aired in Japan on ABC channel from January 8 to March 26, 2014. The series was directed by Yoshiyuki Fujiwara at studio Doga Kobo with script by Fumihiko Shimo and character design by Ai Kikuchi, who was also the chief animation director. Besides ABC, the anime also aired on AT-X, Tokyo MX and BS11 and was simulcast with English subtitles by Crunchyroll and through select digital outlets by Sentai Filmworks. The opening and ending themes, "Tomadoi→Recipe" (とまどい→レシピ, Tomadoi Reshipi) and "Masshiro World" (まっしろわーるど, Masshiro Wārudo), respectively, are both performed by Mikakuning! (group formed by voice actresses Eriko Matsui, Haruka Terui, and Yu-ri Yoshida). The series was released in Japan in 6 DVD and Blu-ray Disc volumes between March 19 and August 20, 2014. The first volume contains a 12-minute-long original video animation episode. A 10-minute-long original video animation (OVA) episode was released on March 28, 2014, bundled with the limited edition of the fifth tankōbon volume of the manga.