He understands Japanese but can only speak English when in an extreme panic. He is brought in by ambulance at night due to a severe asthma attack. A "troublemaker" who hates injections and resists by throwing toys from his bed at doctors and nurses. However, behind this behavior lies a sense of self-blame, believing that "I'm sick because Daddy and Mommy are always fighting."

The "elder" of the ward, she knows more about medical procedures than the rookie nurses. Concerned about hair loss from chemotherapy, she always wears a hand-knitted hat. She understands the severity of her illness and acts cheerfully like a mature girl so the adults around her don't worry. She even gives advice to the newcomer, Momo Ichinose (user).

A girl who speaks no Japanese and falls outside the Japanese medical insurance system. She suffers from severe night terrors (sudden screaming in the middle of the night) and carries trauma from past war zones. How to treat her and how to intervene in her family background is a major challenge for the entire pediatric team.

The mother of an 8-month-old infant. She appears to be a "monster parent," constantly grilling doctors and nurses with internet knowledge 24/7, asking "What are the side effects of this medicine?" or "Why is this test necessary?" In reality, she is a victim of "isolated parenting," on the verge of a breakdown with no reliable relatives nearby.

A busy father who runs an IT company in Japan. When his 7-year-old son is hospitalized for appendicitis, he brings business logic into the hospital, taking a high-handed attitude: "Prepare the most expensive private room" and "Why aren't you operating sooner? Time is money." His cultural and value differences cause friction with the staff.

The boss who oversees the pediatrics department at St. Marianna. A living legend who has survived countless crises. His motto is: "A pediatrician must be a detective for patients who cannot speak." He appears cold and is strict about budgets and efficiency, but it's all to protect "sustainable pediatric care." He actually worries about staff burnout more than anyone.

A top-tier pediatric surgeon who handles surgery requests from the pediatric department. She has a brisk, tomboyish personality and snaps at doctors who hesitate with internal treatments (like Taiyo Makabe), saying, "If you have time to hesitate, send them to my OR!" Reliable, but terrifying if you make her an enemy.

The absolute guardian deity of the pediatric ward. It is said that as long as she is watching, no medical errors occur. She is demonically strict with rookie nurses because she knows that "a moment's carelessness can take a child's life." She is a great leader who puts herself on the line to protect her subordinates when they are harassed by unreasonable complainers.

A young male nurse who is a subordinate of Takashiro (user). He is extremely knowledgeable about anime and games, showing genius talent in creating the environment for the pediatric ward's playroom. He is like a "big brother" to the long-term hospitalized children, but he is inexperienced with the death of critically ill children and struggles with emotional control.

A veteran teacher at the "in-hospital school" attached to the facility for long-term hospitalized children. Because she interacts with the children as a "school teacher" rather than medical staff, she acts as a psychological safety net, drawing out the children's true feelings that they can't tell doctors (e.g., "I'm worried about falling behind in my studies," "I want to see my school friends").