Very short, but threw it out in half an hour. Enjoy.
Lots of people questioned why Moblit did it. Why he stuck with Hanji, his superior, his Squad Leader, when it ould have been perfectly in his rights to realise that by simply requesting a transfer, he would likely be able to escape her and her incessant, unintentional attempts on her own life. Everyone would understand it, sympathise even, and it wouldn't have been the first time that Hanji had lost a personal assistant.
But Moblit didn't do this. He couldn't do this. The fact of the matter was, Hanji meant everything to him. She never realised it. She never noticed. Hell, she barely even noticed when her own life was in danger, so how would she ever notice that her personal assistant, loyal Moblit, had well gone well overdue on the amount of years he had to stay with her, and was there anyway. For her.
"Squad Leader, you're going to end up actually dying!"
Hanji was a wonderfully bizarre woman. She was extravagant, but serious when she needed to be. Her mind was sharp, she was incredibly smart, and Moblit loved all these things about her.
She never noticed, not once. Other people noticed- they asked him, why do you stay with her? Why do you stay all these years with a woman who barely even notices you? Does she even know your name?
Moblit just tended to shake his head to these questions, and he always gave the same answer.
"She needs me." He'd repeat. He repeated it to himself, and he repeated it to the people who asked him those questions, and he wished, he begged with whatever power had kept him alive all these years that one day, Hanji would be repeating it too. That she'd realise that he'd been there for decades, just waiting for her. Too shy to ever breach the subject, even when he saw she was hurting. She never asked for help. She was too strong to ever ask for help carrying a burden.
Except… It was true, Hanji did need someone. Carrying guilt, regret, anger at all her past failures, and she never shared them with Moblit. She didn't even consider him anything but the man who pulled her away from the action and considered him a little boring for criticising her when her eyes glowed manically. He was a restraining force; she didn't even share banter with him like she did with Levi.
So it never surprised Moblit when he saw Hanji returning in the morning from Levi's rooms, looking unrested but pleased. When he saw her sharing a kiss with him. When she reacted with worry that wasn't visible to anyone but the people who knew her best that he'd been hurt.
It never surprised Moblit, even though it broke his heart, when Levi proposed. And Hanji, beautiful, smart, wonderful Hanji, accepted.
He was never going to be more than the assistant, no more than that as he watched his Squad Leader marry the Corporal and said nothing more than 'Congratulations'.