Disclaimer: I do not own Lily, James, or anything else in the HP universe.
It began as an interest in her in first year. She was the new girl, the Muggle-born who was new to everything in the Wizarding world. Her red hair and her green eyes and the fact that she was friends with a Slytherin only increased her unusual appeal to him. At the age of eleven, though, he was not yet arrogant, because he was rather scrawny and awkward-looking. He was only caught looking at her once or twice, watching her smooth her robes and pat at her hair.
It continued with a liking in the second year. He noticed her small quirks, such as twiddling her wand between two fingers and how she brushed her hair only behind one ear and not the other. He observed, though at a relatively safe distance, the way she interacted with Snape and the way she quietly touched his arm when trying to comfort him. He saw the way her face would grow bright red when embarrassed
It grew into a crush in third year. He realized how smart she was, always keeping up on her homework and studies without trouble. He noticed how apologetic her eyes were when he finally asked her to Hogsmeade and she had declined, saying she was already going with somebody. He saw how she was never there at Quidditch games, cheering on Gryffindor with the rest of the house.
It developed into a fancy in fourth year. He watched how gracefully she ate in comparison with his friends, the way the fork daintily climbed its way into her mouth past her lips. He watched as she slowly turned from a girl to a young lady. He noticed how her hips grew and how her figure filled out. He scrutinized the way her whole face grew worried when she chatted with Snape, her eyes falling upon his with a sort of plea.
It became affection in his fifth year. He studied the way her face became red with outrage at his actions and the way her lips moved when she spat out insults against him and his friends. He monitored the way her finger would point at him accusingly every time a harmless prank might have been sent off. He watched how angry her eyes became when he attempted to convince her to go to Hogsmeade with him. The Prefect badge proudly pinned on her chest drew his gaze to her with its silver shine.
He saw the way she would yell herself hoarse in trying to tell him off, though she never succeeded in making him feel bad about what he did. He watched her sitting and talking to new friends, even though she would often catch him in the act. He laughed at her antics when she stomped away after he told her that this anger would pass in time, and only affection would pass.
It turned into an obsession in his sixth year. He watched the way she moved, the way she walked, curves evident even underneath the concealing black robes. He saw the way her wrist gently flicked as she quickly moved her wand through the air, the way her lips would mouth the words of a spell. He noticed how her small feet seemed clumsy at times, as if they were too tiny to truly support her body. He observed how she looked longingly over at the Slytherin table, and he knew that she wanted to have her old friend back in Snape, even though he didn't deserve her.
He monitored the way she cut up her roots and other potion ingredients, her knife chopping down decisively on the table. He saw the way she meticulously measured every single item she placed into her cauldron. He watched as some of the small curls of her red hair stuck to her forehead after the fumes of potion making had touched them. He noticed the way her slim fingers enclosed around the slimy objects without a care.
He saw the way the bottom of her robe gently brushed across the top of her shoe and the way that her hair was always falling out of her ponytail when she pushed it up out of the way. He watched as she held her quill tightly in her grasp, jotting down notes on every subject. He noticed the way she always seemed to be straightening her robes or making sure that her Prefect badge was securely in place or her wand was still in her pocket. He watched as she smiled rather sadly with her teeth not bothering to be exposed.
He stared at the way her eyes always seemed to reflect sadness and the way she always seemed discontent with her current friends and the way she scowled when she realized that the Marauders were up to something yet again. He noticed the way the green in her eyes always seemed brighter under the candles in the Great Hall and the way her lips moved when they formed the word no. He saw the way her scarf was always trailing along after her when the wind was blowing, her never bothering to wind it up closer to her neck.
It finally bloomed into love in both his and her seventh year. He finally realized how truly beautiful she was, both inside and out in a clichéd way. He loved the way her hair had always framed her pretty features and the way it dropped neatly onto her shoulders. He loved the way she was always answering questions in class and the way she showed her intelligence, not in a mean-spirited way but in a gentle, beneficial way. He loved how she attempted to be kind to everybody, even the Marauders nowadays.
He loved the way she spoke so eloquently, like she was wise beyond her limited years. He loved the way she spoke with such conviction, every word dripping from her mouth with full believing. He loved the way she was willing to reach out beyond house rivalries and make friends in different houses. He loved her.
Common sense had told him that an interest would be okay; after all, people were merely interested in other people all the time. Common sense had told him that liking somebody was no cause for concern. Common sense had told him that a crush would pass in time. Common sense had told him that fancying somebody didn't mean that you were bonding yourself to them for the rest of your life.
Common sense had told him that affection for Lily Evans would probably end badly, considering how she felt about him. Common sense had told him that his obsession with her was slightly creepy and that it would freak her out. Common sense had told him that loving Lily, loving her for all that she was and could became, was going to be his downfall and that he ought to avoid to continue doing so.
But when had James Potter ever listened to common sense?