[[caption-width-right:242:Masahiro and Mokkun.]]

''Shōnen Onmyōji'' is a light novel authored by Mitsuru Yūki with illustrations done by Sakura Asagi. The novel is currently serialized in Kadokawa Shoten's ''The Beans'' and currently has 25 volumes, including three short stories and a side story.

A {{manga}} adaptation of the light novels was later produced, written by Hinoko Seta and published by Kadokawa Shoten in the magazine ''Monthly Asuka''. First published on August 25, 2005, the manga is ongoing.

A further {{anime}} adaptation titled ''Shōnen Onmyoji: The Young Spirit Master'', was later produced as well. Created by Studio Deen under the direction of Kunihiro Mori, the anime ran from October 3, 2006, to March 27, 2007, spanning 26 episodes.

The plot of all incarnations is set in the Heian era of Japan and follows Abe no Masahiro. He is the grandson of the great onmyōji, Abe no Seimei, though Masahiro lacks the ability to see spirits. The series follows Masahiro's quest to overcome being trapped in the shadow of his grandfather's image while fulfilling his promise to protect Princess Akiko of the Fujiwara clan and stop the hordes of demons invading Japan.

!!Tropes associated with this work:

* ActionHeroBabysitter: Guren took care of Masahiro when he was young.
* AxCrazy: Kyuuki and his minions.
* BadassAdorable: Masahiro, Mokkun, Taiin, and Genbu.
* BerserkButton: If you ever try to hurt Masahiro.... you better run away, because Guren will totally kick your ass.
** Don't call Masahiro "Seimei's grandson", either.
** Same goes to calling Mokkun a mononoke.
* BigBrotherMentor: Narachika is this to Masahiro.
* BittersweetEnding: [[spoiler: Masahiro manages to save the world and Guren...but at the cost of Guren's memories of all the time they had together. ''Permanently.'']]
** [[spoiler: In the novels Masahiro loses his espiritual sight in the same incident. Guren recovers his memories a novel later, but Masahiro's loss seems to be permanent.]]
* CryIntoChest: Masahiro does this in the novels when he and Narachika are reunited after [[spoiler: the battle with Ryuusai.]]
* DarkAndTroubledPast: If anything, Guren's should count. Masahiro's, too.
* DamselInDistress: Akiko.
* TheDeterminator: Masahiro, Guren, Seimei, and many others.
* GuardianAngel: Guren acts something like this towards Masahiro, whom he's sworn to protect.
* FamousAncestor: Masahiro is the grandson of the famous onmyōji, Abe no Seimei.
* FieryRedhead: Guren. 'Nuff said.
** Don't forget Suzaku!
* [[spoiler: {{HeelFaceTurn}}: Kazane]]
* HotBlooded: Despite his looks, Masahiro is this.
* ICanStillFight: Masahiro uses this a lot.
* InSeriesNickname: Masahiro is "Seimei's Grandson" and Guren is "Mokkun" (and sometimes "Touda").
** Actually, Touda is his original/true name; Guren is the name Seimei gave him.
* Jerkass: Fujiwara no Toshitsugu, though he gets better.
** JerkassHasAPoint: He thought Masahiro was [[ScrewtherulesIhaveconnections using his family's prestige to wriggle out of his job.]]
* KidHero: Masahiro.
* MoralityPet: Masahiro was more or less this to Guren.
* RidiculouslyCuteCritter: The Hyakki-yakou.
* TheLegionsOfHell
* OlderThanTheyLook: Seimei's twelve shikigami.
* {{Onmyodo}}
* OurDemonsAreDifferent
* ParentalFavoritism: Masahiro seems to be a bit favored over his brothers due to his talent.
* PoorCommunicationKills: Oh lordy, [[spoiler: Guren is mind controlled by Ryuusai and almost maims Seimei against his will. Once he snaps out of it, the shikigami come and...assume Guren attacked him on purpose, not even giving him time to clarify/explain the situation! This would have been avoided if they didn't jump to conclusions and actually let Guren talk!]]
* TheResenter: [[spoiler: Masahiro's older brothers are more upset with the ParentalFavoritism than they show. But in this case they are resented only with the situation and both of them really care for Masahiro and love him.]]
* StepfordSmiler: Masahiro after [[spoiler: Guren loses his memories of him.]] He tries to endure it bravely but he breaks down when his brother comes to visit him.
* [[spoiler: {{Yandere}}: Fujiwara no Keiko. Going as far as offering herself to demons, people?]]
* YoungestChildWins: Masahiro is the most powerful of all his siblings.