Author's Note: I wish Kubo would show us how Shinji came to accept Hinamori as his lieutenant. What I wouldn't give to be a fly on the wall for that one. I mean, I can't see myself jumping up and down to inherit her, if I were a captain. But Hinamori seems to have rallied, recently. Until Kubo comes out with the official story, here is one possibility of how it all came to pass.
This is another relatively introspective piece. One of these days, I will write an action story. I think.
Chapter 1: Unknown Quantity
'It feels strange to be back after so long,' Shinji thought, as he stood in the doorway of the 5th Division's office, gazing inside at the room he thought he had left behind forever. Behind him, birds sang in the secluded garden. In the distance, the sounds of his division drifted across the clear blue sky; sounds of shinigami completing paperwork and running administrative errands during this period of relative calm. These everyday sounds told him that all was well. At least, as well as could be expected, given everything that had happened.
In his head, Shinji was lining up the old memories of his office with the new reality. The office looked mostly the same. Most captain offices were austere by tradition, dominated by empty space. Such was the case with his own office. 'Before' (and he wondered in a corner of his mind how many other people in the Gotei 13 divided their lives by the same marker as him: 'before' vs. 'after' Aizen's betrayal), his office contained only 3 pieces of furniture: his desk, his chair and a turntable. The turntable had been his personal possession, and he was sad to see the empty space it used to occupy.
But there, at the left-hand end of the room, was his large wooden desk, worn smooth over years of use until it gleamed a rich, dark brown. It was standard equipment and so escaped the purge after he had to flee Soul Society with a death sentence on his head, 'after' Aizen's betrayal (which, he realized, was a point further back in time for him than for many people). Shinji was sure it was the same desk from over a hundred years ago, the wooden chair tucked up neatly underneath, both still serving dutifully, heedless of the changes in leadership over the years. There were already a few sheets of paper on the desk, held down by a pale blue stone paperweight that he had never seen before. The slim ceramic vase on his desk was also new, a pale turquoise in color, holding a stem of lily of the valley. The little white bells nodded gently in same the breeze that stirred his short blond hair, their soft scent perfuming the air. A fitting decoration for the desk of the 5th Division's captain.
The main additions to the room were the new work desk at the opposite end of the room, equipped with a chair and paperweight, all nearly identical to his save for the fact that they were slightly smaller.
'Me in miniature,' Shinji thought with humor an instant before he realized whose desk that must be. Shiji felt his humor evaporate as he focused his attention, pulling his mind out of memory lane and really looked at the room. The Gotei 13 was short-staffed, no relegating menial tasks to flunkies, since most of the flunkies died or quit after cracking under the pressure. Who oversaw the selection of the matching furniture, of the paperweight and vase in coordinating colors? Shinji felt sure it was Hinamori Momo. He doubted anyone else would have taken the time to think of such details.
Shinji drew a deep breath and at last entered his old (new) office.
'Hinamori Momo,' he turned her name over in his mind as he walked slowly towards his desk. He read her files a few days ago, wanting to learn more about his new lieutenant. He didn't get much of a chance to get to know her during their showdown with Aizen in the skies of the fake Karakura town. Frankly, he thought it was a good thing for her that she was such a capable lieutenant 'before'; otherwise, the Captain-Commander might have consigned her to the Maggot's Nest and called it a day.
"And here is a little sample of that administrative skill," Shinji told himself with some wry amusement as he ran his fingers lightly over the papers on his desk, his sword callous rasping against the pure white sheets. All organized, all in order; easy for a new (old) captain to take over and hit the ground running.
But... he saw the recording of her conversation with Hitsugaya taicho while he was stationed in the human world. It was not encouraging.
'Be fair,' he told himself. Aizen worked on her for years to create the perfect tool that would die without him. But she didn't die. 'Wouldn't die.' Shinji recognized it as a conscious will to survive. That was a point in her favor. But what kind of mind is now channeling that will?
Outwardly, her body had mended. Inwardly… her psyche seemed to be, very suddenly, doing the same, according to Unohaha's reports. This sudden turn for the better made him suspicious. And being stabbed in the chest with Hitsugaya taicho's sword, nearly dying (again) as a result, seemed to have been the catalyst for her improvement. Of all things.
Hinamori, that poor sacrificial lamb, was an unknown quantity at best and a time bomb at worst.
The wind died. The lily of the valley stilled, as if it was waiting.
"Well," Shinji said aloud as he tipped his chair back, balancing it on the two back leg, and stretched, "I suppose I should try to measure that unknown quantity, since I'm a bit of an unknown myself." Using his hands to push off the precariously balanced chair, he sprang through the air and landed lightly in front of the sliding doors. He walked out into the sunshine and slid the doors shut softly behind him just as the chair tipped back, neatly, onto its four legs.