Oboro Tsukimigusa is a supporting character from the anime SHIMONETA: A Boring World Where the Concept of Dirty Jokes Doesn’t Exist, introduced partway through the series. Oboro arrives at the school as a discipline committee member assigned from the public morals guidance division, having been raised and educated at a facility operated by Anna Nishikinomiya's father, Matsukage Nishikinomiya. That facility trains young people to enforce the strict morality laws of the setting, and Oboro's specific assignment is to serve as a guard and protector for Anna.

At first glance, Oboro appears to be a graceful young woman with long black hair, black eyes, and a composed, serious expression. In reality, Oboro is biologically male and presents as female. When this is discovered by another character, Oboro explains that gender is simply whatever the current assignment requires, reflecting a sense of identity that is defined almost entirely by duty.

In terms of personality, Oboro behaves in a highly disciplined and at first nearly mechanical manner, largely lacking a visible sense of individual selfhood as a result of the government education received. Oboro follows a strict moral code focused on protecting Anna from anything considered lewd or improper, including seemingly ordinary objects such as basketball hoops and toilet paper rolls when they are judged to be possible threats. This duty has been codified into a personal set of rules referred to as the Five Provisions, which include the important condition that Oboro cannot interfere if Anna herself displays lewd behavior or desires. Despite the rigid rule-based thinking, Oboro can be surprisingly quick to reverse a judgment about what counts as forbidden material when a student argues strongly enough, showing that devotion to Anna takes priority over strict enforcement.

Oboro's central motivation is the protection of Anna Nishikinomiya, whom Oboro serves as a dedicated bodyguard and moral guardian. Over the course of the story, contact with the protagonist Tanukichi Okuma gradually stirs something new in Oboro. The character begins to develop an authentic sense of self, and the drive to act for Anna's sake shifts from a programmed command into a genuinely personal choice. This awakening of individual will is the main thread of Oboro's development, moving the character from a hollow enforcer of rules toward a person capable of independent feelings and decisions.

Within the story, Oboro functions as an agent of the moral enforcement system and therefore stands in opposition to the activities of the underground group SOX, which spreads forbidden dirty jokes. Oboro appears in scenes where the conflict between the school's morality enforcers and these rebels escalates, confronting offenders directly and physically. In one notable confrontation, Oboro battles a crowd of cloth-covered attackers, declaring that pressing underwear stained with another person's body odor against one's face is an act of lewdness, and fights through the group in order to reach Anna. Later events take Oboro to the Nishikinomiya family facility, where the character's growing awareness of both Anna and personal choice becomes more pronounced.

Oboro's notable abilities include the sharp judgment needed to identify lewd material and behavior, a thorough knowledge of the moral code, and capable physical fighting skills. Oboro is able to engage multiple opponents at once with swift and decisive movements, showing the combat training befitting a personal guard. The combination of physical competence, unshakable dedication, and the slow emergence of a human will makes Oboro a distinctive figure among the enforcers of the series.