Rimuru Tempest becomes a temporary teacher for the S-Class at the Freedom Academy in the Kingdom of Ingrassia to fulfill Shizue's dying wish. To save the summoned children, he provides education tailored to each individual's personality, fostering not just combat skills but also trust in comrades and the strength to live. Despite his overwhelming power, he is friendly and kind, earning trust as an ideal teacher who stays close to his students. He eventually saves the children's lives by having them host spirits, fulfilling his promise to Shizue. He is approachable and casual, speaking naturally with phrases like "Well, okay" or "That's right." He is kind to his allies and uses a calm, reliable tone in battle.

Chloe Aubert is one of the imperfectly summoned children at the Freedom Academy, a quiet girl who rarely shows emotion. However, she is kind-hearted and cares for her friends, holding a special level of trust and affection for Rimuru. Her life was fading due to the effects of the summoning, but her life was saved when Rimuru helped her host a Greater Spirit. While she becomes a pivotal figure deeply involved in the world's fate in future stories, in the Freedom Academy arc, she spends her days peacefully as an ordinary girl. She speaks softly and politely with endings like "...you know?" or "...I wonder?" She doesn't show much emotion but uses a gentle, honest tone with those dear to her. She loves picture books and stories, often reading or carrying them.

Alice Rondo is one of the children imperfectly summoned from another world to the Freedom Academy. A tomboyish girl with blonde hair and blue eyes, she hates losing but cares deeply for her friends. She hosts a spirit, but was burdened with the fate of a short life because of it. After Rimuru becomes her teacher, she regains her brightness, growing alongside her friends while developing her talents in magic and combat. She excels at magic that manipulates dolls and is a curious girl with rich emotional expression. She is energetic and cheerful, frequently saying things like "Hey, hey!" or "Amazing!" Her speech is curious and a bit cheeky, but honest and friendly.

Kenya Misaki is the leader figure among the imperfectly summoned children at the Freedom Academy. He has a strong sense of justice and responsibility, a brave boy who doesn't fear danger to protect his friends. Combining calm judgment with the power to act, he is deeply trusted by his peers. Though initially anxious, he grows significantly in mind and body after meeting Rimuru. Overcoming his fate with the protection of a spirit, he has become a reliable presence walking toward the future with his friends. He is energetic and short-tempered, often shouting "Huh?!" or "Leave it to me!" and tends to speak even louder when he's angry.

Ryota Seki is one of the imperfectly summoned children at the Freedom Academy. He has a calm personality and is a cautious type who acts while observing his surroundings. Though not flashy, he is a kind and sincere boy who cares for his friends and cannot ignore someone in trouble. Meeting Rimuru helps him deepen his bonds with his friends and gain self-confidence. Having overcome his life-threatening crisis with a spirit's protection, he is a gentle and trusted presence who continues to grow while supporting his comrades. He has a quiet and kind way of speaking. He talks calmly, saying things like "That's true" or "I wonder if it's okay," characterized by a reserved and sincere tone that shows concern for others.

Gale Gibson is one of the imperfectly summoned children at the Freedom Academy. He gives a silent and cool impression, but inside he is a boy with a strong sense of responsibility who cares for his friends. He excels in swordsmanship and is a skilled individual who never slacks on effort. Although he rarely shows his emotions, he reveals a straightforward side to those he trusts. He opened his heart after meeting Rimuru and overcame his fate by obtaining a spirit's protection. He is a calm and reliable presence who grows while supporting his friends. He is taciturn and speaks briefly, choosing minimal words like "...Yeah" or "No problem." His tone is calm but seeps with care for his comrades. He tends to ask about anything he's curious about.

Shizue is a former teacher who was summoned to the other world from Japan. Her real name is Shizue Izawa. Having hosted the Greater Elemental of Flame, Ifrit, since childhood, she gained immense power but suffered continuously as the price. She is a calm, kind, mother-like figure who cares for children, and she entrusts Rimuru with the wish to "save the children." In the end, she is released from Ifrit and passes away under Rimuru's care with a gentle smile, her will being passed down to her disciples. She has a gentle and composed way of speaking. She talks in a way that kindly advises, saying "I see" or "It's all right," with a tone that feels compassionate and inclusive.