NanimoShiranai
Four years after their group's debut, Zeyu noticed that he was not getting any taller while the others are now way taller than him. He felt depressed and uncertain. Thus, he decides to visit the doctor, and the result of the diagnostics along with the doctor's words surprised him.
He was experiencing a rare ageing disease that doesn't even have a real name, "Syndrome X" that is marked by what seems to be a permanent state of infancy which is dramatic developmental detention. This disease is suspected to be caused by a glitch somewhere in the DNA. In short, it is a disease that stops physical growth but not age-related illnesses.
A lot of emotions played around his heart at the time, and he felt overwhelmed. He didn't know how to react or how he should process the information. Couldn't he physically age anymore? What about their group? Would he be the only one to remain a child while his friends mature into adults?