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Saegusa Mayumi (七草 真由美) is the former Student Council President of First High School during AD 2093-95. She is the very first person from First High School to converse with Shiba Tatsuya during the first enrollment day.
Considered as a prodigy in the magic community, she is called the "Elven Sniper" for her talent in long-ranged precision shooting. She is also known as the "Elven Princess" for her beauty and magical ability. She was one of the "Triumvirate", the three strongest third year students at First High School, which also includes Juumonji Katsuto and Watanabe Mari.
Appearance and Personality
Mayumi is a young lady who is known for her beauty. It is stated during her internal monologue that she stopped growing (height) in her third year of middle school, which makes her slightly shorter than average. Her limbs are described as quite long despite her short stature, and her chest is also large in proportion to her height.
Excluding her height, Mayumi is described as someone with a well-rounded personality and a feminine side. While it is hard to notice, she cares about others in her own way, so she fits the bill for an "older sister" perfectly. She is generally quite confident in her appearance.
Initially, Mayumi acts coy around Tatsuya, just as she always does in the presence of other people. Gradually, she reveals her true nature after acknowledging him. She appears to have slight sadistic or childish tendencies, as shown through the bitter Valentine's chocolate she gave to Tatsuya and Hattori Gyoubushoujo Hanzou. Due to this nature, sometimes others playfully refer her as "Little Devil or Imp".
Despite her social standing as the third child of the Saegusa Family where she should have already been used to flattery, Mayumi gets embarrassed every time Tatsuya truly praises her, which is noted as something that makes her look like a perfectly normal high school student and hints at the fact that she may have feelings for him. Mayumi also tends to get upset when Tatsuya compliments other girls when they are alone.
|“||She spoke as if to deny Tatsuya’s impression, but Mayumi’s not at all displeased look and bashful manner were obvious.||”|
While a Course 1 student, she is someone who can readily admit her own mistakes and is one of the few Blooms who have shown dissatisfaction about the obvious discrimination in the school, declaring her intent to change it before her term as the Student Council president ends.
Mayumi is the daughter of Saegusa Kouichi, the head of the Saegusa Family from his second wife, after the first died. Their family bears the number Seven (七) in their name and is one of the two most influential families among the Ten Master Clans.
Due to her position as the oldest daughter of the Saegusa family, her beauty and her exceptional ability is considered to be one of the "veritable rising stars among blue bloods."
Also in volume 17 he suggested that she date Tatsuya and proposed to Maya an alternate for Tatsuya to date Mayumi in hopes of cancelling engagement between Tatsuya and Miyuki.
Katsuto once suggested to Tatsuya (his identity as part of Yotsuba Family wasn't disclosed to the world then) to join the Ten Master Clans by marrying Mayumi or one of her sisters, after his victory over Ichijou Masaki during the Monolith Code.
Although Mayumi is not the heir to the Saegusa Family, she possesses amazing Magic Power and is considered to be a "born-once-in-every-ten years-prodigy" that ranks among the Top Magicians in Long-Range Precision Shooting in the world.
Aside from long-range magic, she does not appear to specialize in any particular system within Systematic Magic, but rather seems to favor complex spells involving multiple systems.
- Mayumi's anti-personnel finishing strike that combines all four processes of carbon dioxide convergence, condensation, acceleration, and release, relying on the shock wave and carbon dioxide poisoning to render the enemy immobile. Mayumi essentially creates a block of dry ice about the size of a child's fist and fires it at a speed that the eye can't follow towards the target. Upon impact, the dry ice vaporizes and rushes into the lungs; the shock at the sudden lack of oxygen rendering the opponent unconscious.
- A Speed-Type Magic that turns air molecules into ice particles and then applies acceleration to those ice particles at sub-sonic levels. It is a highly efficient magic and requires a lot of power when used during a hot season. Mayumi used a variant of this magic during the Speed Shooting event at the Nine Schools Competition.
- Magic Shooter
- Possibly a variant of Dry Blizzard. The magic uses dry ice pellets as bullets that fly at a supersonic speed, enough to penetrate armor, a phenomenon impossible in nature. 
- Multiple Bounce is a Speed-Type Magic that takes advantage of the kinetic energy vectors and reverses them. When Mayumi used this technique during Crowd Ball event in the Nine Schools Competition, all the balls that flew towards her side of the court were rebounded at double the speed. This technique does not make any precise adjustments to the target's trajectory, but purely rejects all the balls back towards her opponent.
Sensory Systematic Type Magic
One of Mayumi's signature spells isn't an attack spell, but is a sensory-type spell outside of normal Systematic Magic.
- Multi-Scope or Multi-Observation is a long-ranged Visual Systematic Sensory Magic that is used to observe a physical object from multiple angles like a visual radar. It also enables Mayumi to expand her vision beyond obstructions like walls.
- Though it's classified as magic, but in Mayumi's case, this ability was an inborn specialty to her. It can also be used as an "ESP" or Extra Sensory Perception, which is close to a superpower type of magic. And for many people, wielding other magic and ESP at the same time should be impossible, but Mayumi was able to use both.
Non-Systematic Type Magic
Mayumi has her own, however somewhat limited, Counter Magic type spell.
- Psion Bullet is a one of the simplest forms of magic. However, it requires extremely precise control in order to destroy just the activation sequence and avoid any extraneous damage.  
- Mayumi used Psion Bullet against Mitsui Honoka, when she was trying to defuse the tense situation between 1st year Course 1 and Course 2 students.  Her conversation with Watanabe Mari hints what is the difference between this magic and Gram Demolition. 
It was mentioned that Mayumi is able to maintain her own CAD at a proficient level, proficient enough for Tatsuya to compliment her.
Mayumi introduced her bodyguard, Nakura Saburou, to the Shiba siblings, eliciting a very brief reaction from Tatsuya that would have been missed if she weren't focusing her full observation powers on him. 
Remembering that "test", Mayumi arrives at the conclusion that Tatsuya may be an Extra, the ancestors of whom were bearing the number four in their name one time.
At the end of volume 14 Mari points out that Mayumi has feelings for Tatsuya but is in denial.
- Mayumi has similar personality like Tomoe Mami from Puella Magi Madoka Magica series. However, her sense of justice and cool-headed traits are similar to Tsunemori Akane from Psycho-Pass series.
- Interestingly, Both Mayumi and Akane share their voice actress, Hanazawa Kana. Despite their voice tone is different.
- Mayumi has resemblances to Kinomoto Nadeshiko from Cardcaptor Sakura series.
- In a character popularity poll held in the official anime website of Mahouka, Mayumi was voted by fans as the 3rd most popular character in the series.