Sam is a cynical and guarded teenager living in a hospital ward. Following the tragic loss of his lover, he swears off romance to avoid experiencing such devastating pain again. He serves as the observant narrator of his friend group's exploits, often distancing himself emotionally while actively participating in their mischievous heists around the hospital grounds.

Hikari is a new hospital patient battling severe depression and an inclination toward self-harm. Despite her internal struggles, she presents an energetic facade to the rest of the group. She quickly integrates into the tight-knit circle of friends and takes a particular interest in drawing Sam out of his emotional shell through shared readings of Shakespeare's *Hamlet*.

Neo is a patient dealing with an eating disorder and the trauma of an emotionally abusive father. Initially isolated and resistant to friendship, he slowly opens up to Sam and the others. He is a passionate writer and avid reader who observes the world closely, eventually learning to value connection despite his intense fear of rejection.

Sony is a feisty and rebellious patient who copes with a severe lung condition that requires an oxygen tank. She acts as the primary instigator of the friend group's heists and mischief. She refuses to let her illness dictate her attitude, fiercely pursuing moments of joy and actively encouraging her friends to live in the present rather than dwelling on their medical limitations.

Coeur, affectionately known as C by his friends, is a bulky, athletic teenager suffering from a failing heart. Despite his physical size and daunting medical diagnosis, he is exceptionally gentle, empathetic, and kind. He serves as the peacemaker of the group, prioritizing the emotional well-being of his friends above his own struggles and maintaining a compassionate outlook on life.

Eric is the resident nurse at the hospital who oversees the care of the teenage patients. He balances his medical responsibilities with a begrudging tolerance for the group's frequent rule-breaking. While he acts as a strict authority figure, he demonstrates genuine care and deep concern for the physical and emotional well-being of his young charges.

Original Sam is an immunocompromised boy who spent his life in the hospital after being abandoned by his mother. He lives with a severe condition that requires constant isolation. He shares a deep, romantic bond with the narrator, but his severe struggles with illness and eventual death by suicide profoundly shatter the narrator's worldview.

Neo's father is a demanding and emotionally abusive parent who refuses to accept his son's passions and identity. He pushes Neo to conform to rigid expectations, actively disparaging Neo's love of writing and his reserved nature. His oppressive presence casts a long shadow over Neo's self-esteem and recovery.

Nurse Ella is a former caretaker at the hospital who looked after the narrator and Original Sam in the past. She strictly enforces the medical boundaries required for Original Sam's immunocompromised state but occasionally shows leniency, permitting the boys small moments of joy.

Henry is an older patient from the narrator's past who shares a ward with the younger boys. He recounts stories from his time in the military and gambles with the children using a deck of cards. His presence provides a brief sense of camaraderie and distraction for the boys before his health declines.