grief
Well, he would have the mental disposition toward it since, if I’m recalling some oft he canon material (can’t remember what it was from though…) it said that Hiro suffers from anxiety to some degree. Losing his best friend, his brother, the one person who knew him better than himself and always knew just what to say to him, or do for him, and was alwaysthere
Until suddenly he wasn’t.
How could Hiro put into words his aunt could understand that he couldn’t face all those faceless strangers grieving for his brother? Faceless strangers who may not even be grieving, but came out of politeness. How could he put into words that it wasn’t just the stiff black suit that suffocated him, but the presence of so many unknowns in his home. His sanctuary. The one place he could always go and be understood, because the one person who always understood him was right there, by his side. Always.
He couldn’t put it into words, because Hiro wasn’t good with words, or with people - not like Tadashi is. Was. It was Tadashi who would always explain him to Aunt Cass in ways she could understand. Her very own Babel Fish, set to Hiro-Language.
The days go by in a nightmarish haze he can barely remember. The colour is leeched out of everything. Sounds are muted. Touch can barely be felt. All he can see is the empty space that should be occupied by his brother.
Two weeks after his brother’s death, Hiro has his first panic attack. The scent of burnt cookies wafts up the stairs and under the door to their - his - room. But it isn’t cookies that he smells. It’s fire. Searing hot. Hot enough to burn the tears right off of his skin in hissing wisps of steam. Hot enough to melt the skin from his brother’s body and cook flesh to the bone. Hot enough to burn a body until there weren’t even ashes they could bury.
His lungs burn. He can feel his throat sizzling; melting shut. Not that it matters to him anymore. He doesn’t speak. Hasn’t spoken since the hospital where he screamed his brother’s name until his throat bled and the doctors had to sedate him.
He’s dying. Not from the outside in, like Tadashi, but from the inside out.
At least he would be with his brother.
When he wakes up the next day, exhausted and tired down to his very bones, Hiro looks over at Tadashi’s empty bed.
Another piece of him dies. He wonders how much longer it will take until he can wake up to his brother’s face instead of a silence so all-consuming it’s an effort to even breathe.
Hiro knows there is no place Tadashi can go where he won’t follow.
Hamada brothers stick together.