The first time she loses a patient is not quite one year into her apprenticeship, and afterwards she stares at her hands, washed clean of blood because the hospital has a strict policy and Sakura managed to time her breakdown until she was out of the operation room.

It's her first kill, by rights it doesn't count - she's a ninja and a medic and Tsunade-sama stressed she's absolutely not to confuse failure to save someone with killing, that's how medics burn out and get put on leave.

She keeps the weight of it locked - she builds up experience and performs medical miracles like only Tsunade could and gets blood on her hands the old-fashioned way - she doesn't forget, but she keeps it contained, quiet; until one night years down the line, holding hands like the children they haven't been for a decade, when Sasuke's crimes and Naruto's fears drop like pearls out of their mouths, and hers, too, quiet and safe and better to share than to pretend away.