I decided to participate in CoLu Week! I forgot to post my drabbles for each day here, whoops. Hope you enjoy!
Disclaimer: I don't own Fairy Tail!
Lucy would always study Cobra when Crime Sorciere came to visit. She worked hard to be discreet and succeeded (not that it was hard to go unnoticed in Fairy Tail's guild hall, Natsu's brawling occupied everyone's attention). With all the fighting around her, Cobra was not listening to her soul. Somehow, that both hurt and comforted the Celestial mage as she learned to read the Dragon Slayer's body language.
As she watched him over the course of several visits and analyzed his behavior in the months in between, the blonde learned Cobra's language. Usually shortly after arriving at Fairy Tail, his eye would narrow in annoyance. Lucy could then count down the seconds before he would go and join the brawl that ruined his hearing. He was rather easily annoyed from what she saw, but never truly angry. He avoided the bar, she noted. The explanation was clear when his shoulders would tense in a combination of fear and revulsion around Mira, no doubt a result of her matchmaking and baby fantasies.
So the Stellar Spirits mage learned to detect most of the Poison Slayer's emotions. He never dropped his act of snarky comebacks and a shit-eating smirk, but those small tells were enough. The way his eye softened slightly around his team, the people he trusted and who understood him the most. Lucy felt a twinge of jealousy when she saw that, no matter how hard she tried to push it down. Of course he would feel the most comfortable around his team. Of course he would love them (love is what shone through his eye, she knew because Lucy could spot that emotion the best). Simply because the blonde knew all of this does not mean it did not hurt her to realize that her love for him was unrequited.
She ended up reading Cobra wrong. He had noticed her and he did eventually make his interest in her known. The Celestial mage could not have been happier than the day he finally confessed. But even as her Dragon Slayer acquainted himself with the language of her soul, she kept hidden just how well she had studied his own language. She hid just how fluent she was in his own emotions. After all, Lucy needed to keep a few tricks up her sleeve to surprise him with.