Not just a mission

How?

Lucy walked inside the guild and imediately tripped and fell making a small thud. Everyone turned around and looked at her worried.
Natsu ran to her and helped her up.
"You okay Luce?"-he asked moving his hands up and down her arms. She looked up at him and smiled.
"I'm fine, thanks."-she answered and slowly walked to the bar.
Natsus lightbulb turned on and he raned to the mission board searching with his eyes.
Suddenly he took a paper of the board and went to Lucy confused.
"Hey Luce?"-he called looking still confused at the paper.
"Yeah?"-she said boredly looking at the cup in front of her.
"There's a special mission for us."
Hearing this Lucy turned around and looked at the confused boy who was looking at the paper in his hand.
She got up and stood next to him looking at the paper.
It said: A mission for Natsu Dragneel and Lucy Heartfilia
Dear Natsu and Lucy,
I want you to act as a couple for one week. Your reward will be 1 000 000 jewels. I will be watching.
Lucy and Natsu looked at each other and searched for an answer into other ones eyes.
Lucy blushed and looked away-"What do you think?"
Natsu watched her surprised and also turned his head blushing.
"Well..."-mumbled Dragon Slayer.
Lucy felt looks on her and said they should take a walk.
They were silent until Natsu stopped walking. The celestial mage turned and looked at him.
"You decide. I don't mind the job, but I don't wanna make you do something."-slowly spoke the boy.
Lucy blushed and turned her back to him-"I don't mind."
Natsu looked up surprised and walked to her. The flustered girl looked at him and smiled seeing him smile too.
"So, how do we do it?"
Lucy blushed and took the confused boy to one place she knew with answers: The Library.
Natsu looked at the pictures of couples, read romantic stories, and when all was done he looked at Lucy and asked her:"What now?"
Lucy blushed and slowly answered:"Imagine you and me like that."
Natsus face burned.
*Time skip*
The both mages sat on Lucys bed. They knew what was coming.
"Okay. Let's do this."-the girl spoke first and looked at him.
He was silent. He didn't dare to move.
"Come on Natsu. We slept together before."
"I know, but for some reason I'm nervous."
Lucy blushed and smiled at him softly.
She laid down and patted a place next to her. Natsu laid next to her and slowly pulled his arms around her.
Lucy felt his hot breath on her hair and snuggled close to him.
Somehow they fell asleep.