Requested by HumbleTomato my first request yay!
--------------------------------

He couldn't contain himself, he couldn't stop himself. The part of himself that he hated, yet he didn't WANT to stop. It was all because of his attachment to a (h/c) warrior named (Y/n) (L/n). It wasn't even an attachment, it was an unhealthy OBSESSION. Sometimes he wish he could just take you right then and there, and have you all to himself. He stared at you in a daze at your beauty and fierce expression like it was taunting at his beating heart.

He didn't realize he was staring until you called his name.
"Oh Robin! Want to join in the training!" You called with a happy expression which he found adorable. Followed by the sound of your voice, his ears drinking up the sound of his name. Oh how he wanted to hear it again and again.

"Oh, I'm kind of busy." He wish he wasn't, he wanted to just abandon all of the maps placed in front of him and just run over to you. The sick feeling of embracing you, feeling your bodies touching; the feeling just eating him inside. However he didn't expect you running over to him standing practically next to him, he blushed evidently at your presence.

"Oh? Are these the new battle plans you're working out?" The look of concentration trying to figure out his own tactical plans. He glanced and swallowed roughly to please his parched throat. He coughed slightly trying to compose himself.

"Yes, we need to start making a move." He said simply, trying to play it cool.

"Hmm...these look impressive!" You praised. His heartbeat roughly..you praised him.
'They praised me!' He thought smiling. He wanted to hear it again, the sweet voice saying nothing but praises to him and only him.

"(Y/n)! Could you come over here for a second?" Chrom called.

"Oh sure! I'll see you later Robin!" You bid him goodbye running over to Chrom, the leader of the Shepards. He waved at you, and once you were out of sight his hand fell and clenched at his side. Always, always your attention is driven away from him whenever he gets even 1 second of time with you. It wasn't fair, he loved you. Every single aspect of you he loved, he obsessed over. A part of him held himself back from just slaughtering every single person, for the sake of the Shepards, for your sake.

Just the look of any type of anguish on your face would tear him apart, so he needed to play smart. Do away with the ones who are taking you away in secret, in his own tactical way.
-----------------------------------

The Risen had come again, they were coming in huge numbers. The Shepards had already taken care of a majority. You, Chrom, Robin, Tiki, and Frederick were taking care of the last of them. You skillfully slashed with your steel sword in hand having no problem. Robin was keeping an eye on you from the corner of his eye, teaming up with Chrom against a bunch of Risen.

You wiped your forehead panting hard after quite a fight with the Risen. You had thought you had taken care of all of them, except for a stray one about to attack you behind you without your knowledge. Robin's eyes widened, he prepared himself a Thunder spell to blow the thing to oblivion, even the thought of any harm coming to you awakened a new found rage even he didn't know he had. He was beaten, however, by a certain knight.

"Hey look out!" Frederick called guiding his horse your way. He slashed at the Risen killing it instantly. You breathed out a shaky sigh, and smiled gratefully at Frederick.

"Thank you for saving me."

"Anything for a comrade."

Robin hated the sight that laid before him. HE was supposed to be the one to save you. You were supposed to be smiling at HIM. He clenched his fist again only it shook, the unknown rage building even higher like a volcano ready to explode at any moment. His rage took over him, he couldn't control himself. The Shepards had already started leaving the battlefield all fatigue and ready to turn in for the night.

"Frederick, can I see you for a moment." Robin spoke in his normal voice, but the glare in his eyes and the hidden eeriness he held it could be clearly seen in the dead of the night. Frederick couldn't see it however, Robin was smart enough to wait until everyone left, and to keep his cool until the right moment.

"Sure Robin wh-" Frederick cut himself off as he saw Robin open his book. His Thoron spell at the ready.

"You made a mistake, (Y/n) is MINE." He spoke as he watched his Thoron devour Frederick's body in his vision, leaving Frederick's body laying on the ground; nothing but a burnt corpse. He looked for a moment his eyes blank, no feeling of sympathy, and he trudged back to the camp, one obstacle down.
-----------------------------

The next morning you got up early, you wanted to train yourself even more for any future battles ahead of you. Usually you had trained with Frederick, since he was Chrom's guard he had experience on him and you had asked him to train you. It was unusual to not see him and for you to wait. It was usually him waiting for you. You went up to his tent quietly. You peeked in trying not to wake anyone up, but his bed was empty.

'That's weird.' You thought. You went back outside searching the entire camp, but no sign of him.

"(Y/n)." You jumped at the voice right behind you. You turned seeing Robin, something looked different in his eyes but you didn't concern yourself with that.

"Oh Robin, I didn't realize you were up already." You said a melancholic expression appearing on your face.

"What might be the problem? You look worried." Robin said feigning concern, he knew exactly why.

"It's just...Frederick. He's not in his tent, and I didn't find him in the camp." You said sitting on the ground. Robin joined you pulling off a little grin, and then putting on another facade. He wore a mask of sadness as he put a hand over yours and sighed.

"(Y/n), about Frederick. I'm sorry to say this but...he's dead." He spoke carefully, putting out just the right amount of emotion to trick you into think he was just affected.

"W-What?!" The look of horror on your face pulled at his heartstrings. But he stood firm, he didn't want to be caught.

"Yes, killed by a stray Risen. He was struck before I could save him." He said.

You were at a lost for words, a close friend was dead and you didn't even know until now. Your eyes spilled tears before you could say anything, even if you tried it would only come out as choked cries. Robin wiped your tear stained cheeks with his thumb. THE sick feeling crawled up on him. Your skin was softer than he imagined, even from stroking your cheek.

He slowly pulled you into a hug, savoring the moment. It was only you and him, and he liked it so very much.
"I'm sorry (Y/n)." He spoke in a soft comforting voice smoothing your hair. It felt like silk between his fingers, you were slowly invading his senses. Enveloping his mind, his thoughts were drowned with you.

"It's fine...It just hurts. We were such good friends." You said through your sobs and hiccups. Robin continued to soothe and calm you down for some time. Eventually you calmed down and faced him.

"I'm sorry. I needed to get that out." You said wiping your eyes.

"It's fine (Y/n). I'll always be there when you need help." Robin said smiling sweetly. Your cheeks started hearing up at his sweet expression.

You looked down slightly embarrassed pushing your index fingers together, "T-Thank you Robin." You stuttered.

"In fact how about we spend some time together right now?" He asked. He desperately wanted more time, all the time in the world to be with you.

"Ok, but maybe we should tell Chrom. He won't take it well that's for sure." You said already getting up. Robin swiftly grabbed your wrist exacting a tight grip.

"H-He already knows! I told him!" He exclaimed quickly. He tightened his grip as if you were about to disappear. He didn't want to let go...ever.

"So let me spend time with you to make you feel better." He offered trying to hide his pleas.

"Uh, alright." You finally agreed, a happy smile came onto Robin's face as he started pulling you away from the camp.
--------------------------------

"Hahaha!" You laughed as Robin fell into a nearby creek, he was trying to demonstrate some useful defense moves with his sword, but he made a fool of himself and tripped over his own feet. He sat in the river not occupied with his predicament, but with your laugh; he blushed heavily. Not even the voice of god or goddess could compare to your laugh. You held out your hand your voice still filled with giggles.

"You ok there Robin?" You asked. He grabbed your hand once feeling that smooth, soft skin of yours. It took all of his willpower to contain himself. He stood with the blush on his face, his jacket all wet, but all his attention focused on you. He stared at your eyes looking back at him, sparkling like polished jewels.

'Truly beautiful.' He thought.

"Robin?" You called waving a hand in front of his dazed face. Something in him snapped; he needed you NOW. He suddenly grabbed it pulling you forward and kissing you on your lips. You were caught off guard as he kissed you almost hungrily. He moved his lips against yours absolutely loving the taste of your mouth. He was ecstatic when you started kissing back that he even slowly entered his tongue.

You had no idea why he kissed you so abruptly, and you had eventually given in and started kissing back. But a voice in your head was telling you this was wrong so very very wrong, you two weren't even lovers. Robin continued to devour your lips until he needed air. He pulled away gasping slightly, the both of you a panting mess.

"R-Robin..." You mumbled out his name in shock. You looked at him expecting him to say something. He only hugged you tightly not wanting to let go.

"That was better than I imagined." He said in a shaky voice, you could vaguely hear him chuckle.

"Robin. What exactly was that?" You asked.

"(Y-Y/n) I have something to confess to you." He took in a deep breath, now or never.
"I love you. I'm in love with you (Y/n). Ever since you joined the Shepards. Everything about you, your smooth skin, your shining hair, your joyous laugh that was able to cheer me up every time I was saddened. Everything, so please (Y/n)." He placed your hand on his chest you could feel his erratic heartbeat.

"Will you accept my love? I will try my hardest to make you the happiest person alive." He said almost pleadingly. Your face was entirely red and extremely hot. You were very flattered from everything he said. You heartbeat was matching his as you smiled taking his reddened cheek.

"Of course Robin." You said. He looked ready to burst as he dove in catching your lips in another kiss. You two parted after a minute.

"You're finally mine." He whispered. He accomplished what he wanted, you were his, HIS.

"(Y/n)! Robin! You out here?!" Chrom's voice rang throughout the air. Robin grit his teeth as the moment was ruined by his accursed leader. He didn't want to let you go yet, no never, he never wanted to let you go. He never wanted you to go back to the camp. He wanted to take you and run, take you away from anyone who could take you away from HIM.

"Is that Chrom? Hm, we must've spent too long away from camp." You said.

"Come on Robin!" You exclaimed pulling at his hand, but he stayed glued where he stood.

"Not yet.." He mumbled.

"But Chrom-"

"SCREW CHROM! YOU'RE NOT LEAVING WHEN I JUST CONFESSED!" He screamed out suddenly, you were taken aback. He gripped your hand it felt like he was breaking your bone.

"R-Robin.." You stuttered scared and a little in pain. A sudden force to your head caused your vision to blur. You saw Robin with one of the scariest glares in his eyes. He looked crazy, obsessed, lost of all sense of thought. Robin stood looking menacing with an Arc Fire tome in hand. He wasn't about  to let you get taken away that easily. Robin had lost himself, he had snapped.

"I'll kill anyone in the way of our love." He let out a laugh smiling down at your unconscious form.

"You're only...MINE."
------------------------

A/N: Done! Did I fulfill your expectations? What a way to kick off this book with a Yandere one shot. Also all my one shots are with a gender neutral reader unless I say otherwise so you'll see pronouns like they,them,etc.

Next up:

Grell x reader

L x reader

Yandere!Keith x reader