Levi and Hange were very close. Of course Levi wasnt very used to "being close" with anyone so he still is pretty cold despite caring immensely. Hange on the other hand just enjoy's being around him, despite their very chaotic personality that always puts Levi on edge. When their alone they just exist quietly or banter its a relationship without a label or a distinct necessity...something simple that puts them both at ease with each other.

Then you happened.

While most recruits are 16 and up you, Eren, Mikasa and Armin were exceptions to be joining at 15. Which wasnt much of a difference except for brain development and laws but you specifically warmed up to Hange a lot being their assistant and all...but everything changed when they introduced you to Levi jokingly saying that they were "adopting you" because of your lack of parents...to which Levi took it seriously.

Because of this Levi had started becoming much stern around you. If you made a mistake he'd make you do it again and again and again even after everyones left. He'd make you tea randomly, he'd try to find you every time at 8PM to make sure you went to bed and if you didnt he'd threaten to call Hange. Of course Hange was shocked at Levi taking them seriously but completely leaned into it...so technically they adopted you...congrats.

At the moment Hange was in their science lab doing the most random shit with titan blood under a microscope...but the time was approaching 8PM and Levi had descended from his office to start looking for the "offspring" (you)