He was only a boy; not even a teen, only twelve years to his life. He had killed before, but for good reason. He could not claim the senseless, violent murders of his own family as self defense.
Inigo remembered the events clearly as day, if not clearer. He could see their dying faces around every corner. He could physically feel the motions of slitting his sister's throat, of stabbing his mother, of beheading his father. Lucina's acceptance and forgiveness, Olivia's begging and crying, Chrom's curses and anger. Events he couldn't control; events he couldn't take back. Naga would damn him to hell the same way the Exalt did before his untimely death.
The throne room was a place the young boy tried to avoid; it served as a painful reminder of what he had become, and what he had done. Inigo had never wanted the throne to begin with; he was happy with being secondborn, happy being second in line. He didn't want the throne unless he needed to take it. But the Falchion was at his side, the crown was on his head, and the people—well aware that something was wrong with his ascension—cowered.
It was to the point where Inigo didn't know or care if anyone else knew the truth about what had truly happened. His life was empty and worthless; a constant state of dissociating from himself in hopes of waking from a nightmare and seeing his mother, father, sister, aunts, uncles and cousin at the breakfast table. He'd see each of their smiles and offer one in return as they basked in each other's familiar warmth. But it all remained only in a memory; an unreachable dream in his sleepless nights.
His days wandering the dreary halls of the palace were empty, the silence and misery hanging heavily in the atmosphere. Every day was the same, rotating in an endless, unbearable cycle. Everything melted together until Inigo couldn't even feel the passage of time; perhaps this was the warranted damnation for the blood on his hands. His own personal purgatory, and oh how he deserved every despicable, eternal moment of every cursed, eternal day.