Jin sat by Shion's bed on the Elsa, holding her hand and just staring at her. She was dying. His sister was dying. He'd known it for awhile now, and it still didn't seem real. And he, the doctor, the spy, the swordsman: he could do nothing. All these years, all his work, and he still couldn't save her.
And could he? Could Kevin really save her? Jin had stopped her, prevented her from going to him, because he knew what kind of man he was. Power-mad, ruthless, willing to stop at nothing, and ultimately responsible for the death of their parents. Willing to destroy the entire universe for power: the dream of a madman.
But... could he, would he, save Shion? Truthfully, Jin didn't know. He was a Testament; he had defied death and returned. They sought to fight U-Do and if U-do was killing her... So, maybe he could. It was possible. Jin had taken a chance, kept her away from Kevin Winnicott against her will, even though she loved him, had not let her aid his mad quest. But the cost would be her life and, madman or no, the Red Testament (Jin wasn't fool enough to believe there was really that much of the man left inside that body, not really, no matter how ruthless he had been) might have saved her.
When she woke, opened her eyes again from a faint that might be the last before she slipped into a coma, forever beyond his reach, Shion refused his comfort. All his years, all his work, it had availed him nothing and left him not only helpless, but unable even to offer the comfort a brother should be able to offer. Too much time spent learning, righting wrongs, investigating, and not enough time just being her older brother. And now... now it was too late. He deserved her rejection. Somehow, he had been so focused on his mission, he had forgotten the reason for it.
So Jin did the only thing he could: he left her. Left her to the only person – no, not even a person, the only thing Shion would accept comfort from now. And as he watched KOS-MOS go to Shion's bedside, saw her respond and wrap her arms around the android, he hated her.