[3][4][5] Suddenly finding himself in the Sengoku period, average high school student Yoshiharu Sagara is about to be killed on the battlefield.

Yoshiharu notices differences from what he remembers from his favorite Sengoku era video game – Nobunaga's Ambition.

He serves Nobuna with hopes of saving her from Nobunaga's fate to be killed at the Honnō-ji Incident, not thinking of his way back home to the present-day world.

In addition to Nobuna's jealousy to other female daimyos attracted by him, two other persons who have historical foreknowledge hinder Yoshiharu's way.

Yoshiharu and Nobuna strive to overcome the problems, achieving her ambition of the unification of Japan and start trade and diplomacy on the equal footing with European nations.

A museum in his hometown holds an exhibition featuring Nobuna Oda – the woman who unified Japan and played an important role for the international society of the Age of Exploration.

The Ambition of Oda Nobuna is Mikage Kasuga's first work started in 2009, which was inspired by Noboru Yamaguchi's The Familiar of Zero (2004–2017).

Like Saito summoned to Halkeginia as Louise's familiar, Yoshiharu slips into a Sengoku world and becomes Nobuna's retainer.

Kasuga[6] recalls that such plot deviated from the pattern of those days' light novels in which someone came to a present-day Japanese school.

[13] Tatsuya Tamai[14] regards this novel as a composition of superficial and fragmented knowledge on history that readers would have shared through video games or school textbooks.

For the figure of Danjō (Hisahide Matsunaga) in particular, Kasuga[8] acknowledges Reimei ni Somuku Mono (黎明に叛くもの) by Haruaki Utsukibara (宇月原晴明) in 2003.

In addition, mentioning bloody conflicts between brothers of Sengoku daimyos depicted in NHK Taiga dramas, Kasuga[6] explains the motivation toward revising history to avoid such tragedies by changing their gender.

[1] Such characters as Dōsan Saitō, Yoshimoto Imagawa, and Shingen Takeda survive the historical events in which their counterparts in the real history died, making differences in what subsequently occurs.

[11][13] According to Tamai,[15] character settings are the key to the composition of the fragments of knowledge to make up The Ambition of Oda Nobuna as entertainment contents.

People in Kasuga's parallel world show differences from those in the real history, keeping their identity in trivial aspects.

[13] The story tells how female Nobuna accomplishes her ambition of the unification of Japan in several years (Yoshiharu's monologue in volume 19), in which male Nobunaga failed after his thirty-year struggle, and how she then participates in global politics.

In addition to daimyos and their retainers, the author features a wide variety of characters: the empress and court nobles; merchants; mercenary soldiers; religious groups; and experts in literature, art, and tea ceremony.

The last four volumes of the novel even introduce 16th century European political/military figures such as Elizabeth I from England, Don Juan de Austria from Spain, and Maurits van Nassau from the Netherland (as female characters), who never visited Japan in the real history.

Although not included in the list below, the following people were also baptized: Mitsuhide Akechi (Gracia), Kanbē Kuroda (Don Simeon), Ujisato Gamō (Leon), and Yukinaga Konishi (Agostinho).

After the Ōnin War, the Miyoshi had gained its power and effectively ruled Kyoto and its surrounding areas over the Ashikaga shoguns.

Amid rising tensions between Oda and Honbyō Temple, they hold a soccer (南蛮蹴鞠, Nanban kemari) game, instead of war.

Based on the Aki Province, they effectively control almost the entire Chugoku region and the Seto Inland Sea through the alliance with the Ukita clan and the Murakami Navy [ja].

The Ambition of Oda Nobuna began as a light novel series written by Mikage Kasuga (春日みかげ) and illustrated by Miyama-Zero (みやま零).

The author evaluates the original story as lacking coherence, especially in volumes 6 and 7, because they were written under a bad mental condition caused by the shock of the 2011 Tōhoku earthquake and tsunami.

As well as the original story, this spin-off volume has a revised version published in September 2015 by Kadokawa (Fujimi Fantasia Bunko imprint).

Another spin-off story featuring Shingen Takeda and Kenshin Uesugi, titled Ten to Chi to Hime to (天と地と姫と) had been serialized on the free novel website "Fantasia Beyond" by Fujimi Shobo since June 2014.

The Editorial Department of Fantasia Bunko published an official character book in 2017, with illustrations by Miyama-zero and Ryosuke Fukai.