Prompt: Adrien's territorial cat instincts kick in when he sees Nathaniel flirting with his girlfriend in class.

"Alright class, you have the next hour to work on your group projects!" The teacher announced as the students began getting into their assigned groups.

Adrien was put in a group with Kim and Mylene while Marinette was put in a group with Nathaniel and Rose. He wished that he could've been put in the same group as Mari but sadly, his bad luck didn't let that happen. Marinette, on the other hand, wasn't super upset about not being with Adrien because she was already dating Chat Noir. She was slowly talking to Adrien more and more which seemed to make him very happy.

"Marinette?"

Hearing her name caused the girl to spin around and almost collide with Nathaniel, who was extremely close for some reason. "Oh! Sorry Nathaniel!" She apologized quickly and bent down to pick up the book he had dropped. He reached down at the same time and the two bumped heads together.

"Sorry." They both muttered simultaneously. The two blinked at each other for a few seconds before collapsing to the ground in laughter. The noises caught Adrien's attention and he was not very happy to see his girlfriend on the floor, laughing with another guy. Especially since this certain guy had a crush on her. He felt a strange kind of knot tighten in his chest.

He watched Nathaniel stand up and hold out his hand for Marinette to take. She politely accepted with a gentle smile as he helped her off the ground. "Are you okay?" the boy asked sweetly. Adrien wanted to gag but prevented himself from doing so.

"Yeah I'm fine!" He watched his princess reply with a slight blush on her cheeks. He felt the knot tighten. Then, the blonde nearly gasped when he saw that sneaky tomato head stick out his foot to trip Marinette. She stumbled and began to fall but he swiftly swung her around and prevented her from hitting the floor. "Gee Mari…" He spoke as his eyes gleamed down at her in affection, "You really need to stop falling for me."

Adrien couldn't believe his eyes! Was Marinette blushing?! He knew he needed to do something.

"I..uh-" He heard his princess stutter, still in the arms of Nathaniel. 'I need to transform to save her! When I get my hands on that boy I'm gonna-'

"Alya!" He turned his attention to the teacher who was standing in front of the young reporter's desk, holding out her hand. "Give me your phone!" She demanded in a stern tone.

He watched Alya place her phone in the teacher's hand. "Sorry ma'am. I'll update my blog later." She mumbled while refusing to meet the woman's eyes. He watched her stow away the device in a drawer in her desk and then turn to the class. "Students, I need to leave the room for a few moments. I should be back in about 10 minutes and I want everyone to work hard while I'm gone." She announced while heading for the door.

Adrien jumped out of his seat and chased after her.

"Ma'am, may I be excused to go to the washroom?" He asked politely when he had caught up to her. She agreed and let him go. Adrien raced to the washroom as fast as his legs could go and transformed as soon as he shut the door and checked to make sure the room was empty.

..

"What's wrong Mari? Am I too much to handle?" Nathaniel purred in a flirty voice causing the girl to blush deeper. "N-no..I-I mean c-could you please let g-go..?" Her voice quivered nervously.

"Of course.." He smirked, "Anything the princess wants."

SLAM

Everyone's heads turned to the door, where an extremely angry Chat Noir stood. "She is MY princess! NOT yours!" He growled while glaring at the boy who immediately let go of Marinette. She fell to the ground and landed on her back painfully.

"Chat Noir!" Alya squealed. "Can I get an interview with you as soon as I get my phone back? Please?" She begged but he wasn't paying attention to her. He raced to the bluenette's side and carefully brought her back to her feet, not letting go of her in the process.

"Kitty?! What are you doing here?" She questioned frantically, eyes darting around the room as her classmates all stared.

"W-what's going on?" Nathaniel asked. Chat let go of Marinette and slowly stalked up close to the trembling boy.

"I don't ever want to catch you touching my princess ever again. No one is allowed to touch her except me. She is MINE! Do you understand me?" His voice was cold and intimidating. The boy couldn't find the words to speak so he just nodded his head while squeezing his eyes shut in fear.

"And if I do…" He let out a low chuckle, "I'm gonna hunt you down and when I find you I'm gonna-"

"CHAT NOIR!"

He spun around to face the stern look on Marinette's face. "Stop this right now." She said while crossing her arms over her chest. He shot one last threatening glare at Nathaniel before striding back over to the girl. "Good kitten." She giggled while giving him a little tickle under his chin. He leaned into her touch and immediately let out a loud purr.

"You need to leave now- WHA? Chat Noir!" Marinette screeched as she was suddenly swept off her feet and was now flung over her boyfriend's shoulder while staring down at his leather-clad butt.

"Let me down!" She whined. "Sorry princess, but I can't leave you here with this boy after he tried to steal you from me." He declared as he started making his way down the stairs.

"Aww! That's so cute! He literally swept her off her feet!" Rose cooed. The rest of the class still stared in shock as the super hero headed for the door with their classmate. Marinette's face was a deep crimson red.

"Oh and by the way, none of you are to speak of this little incident ever again." Chat informed the class just before he grabbed the doorknob, holding Marinette's legs with his other hand.

"You're such a bad kitty." He heard her murmur just before he felt her tiny hand smack his derrière. "Meow-ch!" Exclaimed as the class tried to stifle their giggles. "Oh you bad princess.." He purred and brought his hand down on her own butt.

"Ow!" She squeaked of surprise. He chuckled and swung the door open before walking out, slamming the door behind him.

Everyone looked at each other and began to whisper as soon as they left. "Yo! Nathaniel!" Alix called from across the classroom. He looked at the grinning girl. "You better stay away from the princess." She taunted.

He felt his face heat up as he swallowed hard, only able to nod his head in understandment.

BONUS!

"Kitty, that wasn't very nice." Marinette scolded after he set her down on her bed. "You've been a very naughty kitten lately."

"Ooh a naughty kitten you say?" Chat purred while leaning closer to her face. "Do you think I need to be….pun-ished"

His girlfriend smirked. "Oh yes kitty~" She grabbed the bell on his suit and yanked him forward. "Which is why you get no more kisses for a week." She whispered in his (human) ear.

His scream of disbelief could be heard all the way back at the school.

I also wanted to say thanks for all the lovely reviews! Hope you enjoyed this chapter!