Armin Arlert
Armin jolted back, flustered.
"Y-Y/n! What are you doing!?" - He spoke. His face is painted bright red and he holds his book to his chest as if it's a shield, he can't make eye contact and is still stuttering.
Mikasa Ackerman
She grabbed your collar and threw you across the room. She looks at you with an expression of disbelieve, disgust and confusion. The only thing that's stopping her from outright murdering you right now is her inability to wrap her head around what the fuck just happened.
Eren Yeager
His reflex kicks in and he nearly broken your nose with his elbow.
"OI Y/N WHAT THE FUCK????" - His face is flushed from anger and embarrassment. He does not lessen his glare nor look away as if he expects you to do it again.
"Hey answer me Y/N!! - He yelled loudly.
You turned back to meet with Mikasa cold/outraged/disgusted/disdainful/murderous/jealoused expression.
Looks like Eren's not getting his explanation.
Levi Ackerman
He second he realized what you were doing, he grabbed the back of your shirt and flung you across the room. You probably broke something.
"Oi oi oi." - He started slowly. - "What in the actual fuck do you think you're doing?" - He sounded calm. Too calm in fact. His face gives a more accurate insight to his true emotions though. Disgusted. Repulsed. Confused. Angered. Hatred. Murderous. And a wide variety of negative emotions more that you're not mentally stable enough to name right now.
He approached you, pulled you up by the collar, only to punch you down the ground again. He adds a kick to the stomach just to be on the safe side.
He spoke again with that eerily clam voice of him: "Go report to Erwin yourself you little piece of shit and hope that my control over my desire to cleanse the world of filthiness doesn't fail to oppress the need to smother you in your sleep tonight."