Lily Shiraishi is the Student Council President of Constant Magic Academy. She is a petite girl with short blonde hair and blue eyes, and she is almost always seen wearing a dark, pointed witch's hat that has a face on it; the face reacts to her current mood, giving an outward sign of her feelings. Despite her small stature, she is one of the most capable and skilled fighters in the entire academy.

Her personality is enigmatic and secretive. She often appears to know more than she reveals, and she conducts herself with a calm, self-assured demeanor that suggests she is always thinking several steps ahead. She has her own strong sense of justice, and she is not outwardly bothered by the prophecy that Akuto Sai will become the Demon Lord, though she privately does not want that future to come to pass. She can become fiercely enraged if anyone comments on her short height, and this anger dramatically amplifies her combat power. Her expression can shift quickly from playful to serious, and she is capable of intimidating even hungry man-eating beasts with a glare.

Her motivations are closely tied to her role as student council president. She works to maintain order within the academy and carries out her duties with a sense of responsibility. In some versions of the story, she also seeks to preserve the legacy of the previous Demon King on behalf of the government, suggesting she has a deeper, more politically driven agenda. Over the course of the series, she develops a romantic crush on Akuto, eventually becoming the first girl to kiss him—giving him a reward kiss after he wins one of her games.

In the story, Lily first appears as a superior to Akuto, since he serves on the Disciplinary Committee under the student council. She tests his abilities early on, and in the manga she defeats him decisively and makes him train at her house with the other girls serving as maids. In the anime and light novel, she is portrayed as kinder and more caring, though still firm when she needs to get a point across. As the series progresses, she becomes a key ally and love interest, supporting Akuto even as his demon king powers awaken.

Her personal development is subtle but noticeable. She begins as a distant, almost authoritarian figure, but gradually reveals her softer side and her genuine concern for those around her. She learns to trust Akuto and work alongside him, and her initial secrecy gives way to a more open partnership.

Lily's notable abilities center on her unique combat style, which involves stretching her limbs like rubber to deliver devastating punches from unexpected angles. She can create afterimages with her punches, attack pressure points with pinpoint precision, and generate a sphere of countless punches that decimates entire armies, a technique called Sphere Smash. Another technique, Knight Slayer, allows her to grab an opponent and use them as a club to beat others. Her Fatal Technique twists her arm like a screw for a precise, deadly strike, and the Big Punch involves wrapping her arms around her body, spinning at high speed, and breaking the sound barrier to deliver an overwhelmingly powerful blow. Beyond physical combat, she is a skilled magic user. She can manipulate air to create tornadoes, use telekinesis to control mana and cancel long-range attacks, project energy balls, and even knock away blinding smoke magic. She is also proficient with incantation guns and a bazooka. Her keen senses allow her to hear heartbeats and motors, and she is a gifted analytical fighter who can predict enemy movements and exploit the weak points in formations.

Overall, Lily Shiraishi is a complex character: a capable leader, a formidable combatant, and a gradually softening figure whose hidden depths and growing affection for Akuto make her an important part of the story.