I can't think of anything other than psychological trauma really, but why trauma from explosions would make you stop speaking is beyond me. Maybe it was trauma from not being able to act? Idek
It's possibly from massive smoke inhalation. The smoke from fire can be just as dangerous and cause severe damage internally. It might've damaged his vocal cords.
And trauma works in mysterious ways.
I think little bro cut his throat. All the weird panels of his throat looking fine, but a person holding a knife. Then a panel of little bro cutting apples wondering if his brother wanted to die along with his acting persona, then little bro holding a bloody knife.
Okay so, Hiroki, Sakuma’s bro got burned from the explosion and everything, how did it happen that his speech got also affected? I understand that his hearing could be impaired, giving that the impact of the fire touched his side first, can someone explain? Does this already happened irl?
I like how the author modeled the brother story from stars