When Levi was just six years old, his parents died from venturing to the outside world. Levi's dad was the commander Survey Corps, being the most powerful soldier with intelligence and skills. Levi was abused as a child. His "so called orphanage guardian" who was a middle aged man around the 40's drank every day/night and barely had enough food to fend for Levi and himself. So, in order to survive, he encouraged Levi to steal from others to get food. Levi knew this was wrong but his guardian insisted that he did or they would both die. So, he stole but barely got his share since the man ate most of it. He lived in the front of the house near the cattle where he lived most of his days as a child. The dirt and filthiness being in the outermost walls really influenced him growing up. He envied and hated the people in the inner walls who lived comfortable lives. Something in him told him to run away, he was sick of it all. Being abused, living in filth, worst of all, being alone. He decided to run away and live on his own. He didn't need a guardian. Soon, he began stealing for a living to survive. His skills and talents spread through the criminals as he was so proficient at stealing and beating up others to get food. He became well-known and the criminals took him in without hesitation. Levi soon became the leader of the criminals (hint getting his skills/talents from his dad). The first thing he wanted to do was to clean up all the dirt and filth among Wall Maria since he despised the way the rich people lived without a care in the world. Eventually as he got older, he became a clean freak and has a soft side for orphan kids because he was like that one point in his life, growing up.
"I've finished cleaning the upper floors, sir. Where am I sleeping?" Eren asked the corporal.
"You are sleeping in the basement." Rivaille said.
"The basement again?" Eren asked.
"Of course. You can't exactly control yourself. This was one of the rules we had to agree upon to take custody of you." Rivaille replied.
"I will go inspect the rooms. You start cleaning here, Eren." Rivaille said.
"Y-yes sir." Eren replied as Rivaille left the room.
Petra came along and chatted with Eren about how Rivaille worked as a famous underground thug before he was admitted to the survey corps from Commander Erwin which surprised Eren.
"Why would someone like that-?" Eren asked, before Petra cut him off.
"I don't know the details." She said.
"Oi, Eren!" Rivaille said, surprising Eren.
He quickly got into his position to give his respect. "Y-yes sir?!" He asked.
"That's no good, redo it from the beginning." Rivaille said, angry.
So Eren went back upstairs and started to clean the rooms like Rivaille had ordered him to. After about half an hour of cleaning, there was a sudden knock on the room's door he was in.
"Eren, come with me!" It was Hanji-san. She grabbed Eren and Eren followed her, with hesitation.
"U-um Hanji-san, where are we going?" Eren asked, curious.
"You'll see." She replied with a smirk.
"Are we going to Corporal Rivaille? He doesn't like other people bothering hi-" Eren said but was cut off by Hanji-san.
"Shhh, look over there". Hanji said, pointing to the kids.
At first, Eren didn't notice anything there except there were kids running around.
Then Eren noticed Levi was near the stove and he looked to be...cooking! Eren's mind spun with questions. Why was Levi cooking? Did he even know how to cook? What was he doing here?
"See that's Levi. He's cooking for the kids." Hanji-san whispered to Eren as she pointed to Levi. Eren nodded dumbfounded; he didn't know what to say.
"He's here often; he likes kids." Hanji-san continued.
"I never knew that. He doesn't look like the type to like kids." Eren said.
"Looks can be deceiving, can't they?" Hanji-san commented.
Eren and Hanji-san continued to watch Levi. Eren noticed one of the kids going up to Rivaille and clinging to him. Rivaille kicked the kid away. The kid went away then came back later and clung to Rivaille again. Again Levi kicked him away. Eren felt sorry for the kid, and wondered if Rivaille really did like kids. Again the kid came and clung to him. Rivaille kicked him away and said, "Yui, I am cooking, I'll play with you later; so leave alone for now!" The kid sulked away, and Rivaille sighed. Eren realized that Rivaille probably really did like kids, it made him happy to learn about this new side of the corporal.
"Hmm this is getting boring; let's make things interesting." Hanji-san said with a devious smile. Eren didn't like the sound of that.
"What are you planning now Hanji-san?" Eren asked. Hanji-san smiled evilly and didn't answer instead she pushed him into the room where Levi was and ran away.
"Wha-" Eren began but didn't finish.
"EREN!" Levi shouted.
Eren turned to face him knowing things were going to end up sour now.
"WHAT ARE YOU DOING HERE?" Levi yelled at him. Eren began stuttering out his explanation.
"Y-you..see..H-hanji-san..she pushed..m-me in he-he-re." Eren finally managed to say. Levi still looked mad and his glare deepened once Eren had explained. Eren flinched afraid of what Levi might do.