The song mentioned is Candy - Paolo Nutini. There are also some references and/or direct quotes from The Fault in Our Stars by John Green.

Kurt can't remember the exact moment he stopped hating Sebastian Smythe, but he can remember the exact moment he fell in love with Sebastian Smythe.

There has only been one quote that has ever described the way Kurt fell in love with Sebastian; it said 'II fell in love the way you fall asleep: slowly, and then all at once." That was how Kurt fell in love with Sebastian Smythe. That is how he remembered it.

Kurt fell in love slowly when he saw Sebastian Smythe out of his uniform for the first time. There had been Scandals, but that was different. That wasn't Sebastian, that had been his alter ego, the one that pretended to not have any worries, no fears, and no cares. This Sebastian was the one who sat in a booth in the Lima Bean, surrounded by papers, a black beanie in his hair and glasses perched on his nose; a black cardigan on his shoulder, and a green t-shirt with a faded design. This was the Sebastian that had looked up at Kurt with a grateful smile when he heard Kurt offer to help him with his Economics homework if he promised to keep the princes jokes to a minimum. He fell in love slowly as he plowed through all of Sebastian's homework, and then ended up writing half his essay as well. He fell in love when he looked up from Sebastian's laptop and saw Sebastian staring at him. "You're something else, you know that?" he had said, and Kurt had blushed, because that was maybe the best compliment anyone had every given him.

Kurt slowly fell in love with the way Sebastian dressed all together. Kurt would never be seen in faded t-shirts or skinny jeans that weren't glued to his legs. He could never wear plaid button down shirts, or green converse, beanies and thick glasses, but he could never get enough of Sebastian in them. The difference between his clothes and his uniform were uncanny, and every time Kurt saw Sebastian wearing another pair of sneakers or Toms, a black beanie on his head, he had a sudden urge to burn the Dalton Uniform just to make sure he never saw Sebastian wear it again.

Kurt slowly fell in love with Sebastian when he first saw his room. It came as a shock when Kurt first entered Sebastian's room and saw that it was nothing close to what he could have ever imagined. A slanted roof, a huge bed, a wall entirely covered by a window. Tea cups, and mountains of books, all with bookmarks and sticky notes, highlighters thrown over some of them, on the floors, on the bookshelf, on the table, even on his bed. Posters, quotes, drawings all stuck haphazardly on a pinboard, a television on a stand surrounded by films in foreign languages. Sebastian smiled as he watched Kurt look at his room, telling him he'd be back in a minute, and when he came back, he found Kurt lying on his rug in the middle of the room, looking up at the slanted window that made its way to the roof, almost glowing in the sunlight. Sebastian put down the coffee mugs on his table, and moved to lie down next to Kurt, where they spent the rest of the day in comfortable silence.

The next few months of summer were spent in Sebastian's room, on the bed, on the rug, sitting on the window seat or lying outside on Sebastian's slanted roof, talking, their conversations easily slipping into French, watching movies with subtitles, and organizing the hundreds of books, magazines, and dvds Sebastian had.

Kurt slowly fell in love with the way Sebastian smoked. He despised cigarettes before Sebastian; he hated the smell, the way they left ash everywhere, the burn marks that got everywhere. But he was falling in love with Sebastian, and he couldn't help but love everything about him, even smoking. He loved the way Sebastian tried to do it discreetly at first, so that he wouldn't make him angry, but then started to do it in front of him, ignoring Kurt's protests with a roll of his eyes, and another drag. Sebastian started smoking even when his arm was wrapped around Kurt as they watched movies on Sebastian's computer, his calloused fingers rubbing circles on Sebastian's arms. Kurt fell in love with the smell, because it was discreet when it came to Sebastian, a faint lingering smell, that he could only smell if he buried his nose in Sebastian's skin.

Kurt slowly fell in love every time he and Sebastian went places other than Sebastian's room. He fell in love with the way Sebastian would slowly slip his hand into Kurt's, at the mall, at bookstores, at flea markets. He fell in love with Sebastian's willingness to go wherever Kurt took him, from festivals to restaurants, to grocery shopping for dinner, to gift shopping. Kurt fell in love with the way he felt at ease texting Sebastian to come pick him so that he could run errands, and how he could change the song playing in the car without any protests from Sebastian.

Kurt fell in love all at once when he found out that Sebastian's fingers weren't only calloused because of cigarettes.

It was the end of summer when he and Sebastian went to a small bookstore that doubled as a café, hours outside of Lima. It was small, and littered with books and couches, and reminded Kurt of Sebastian's room.

Kurt sat at the table, watching Sebastian talk to an old lady before moving behind the counter, and taking out a guitar. Kurt eyed him quizzically, watching Sebastian wink at him before he made his way to the stage that had been set up on the side, where live music played.

"This is for Kurt," Sebastian murmured into the microphone. "Who's moving to New York. He thinks he's leaving me here, but what he doesn't know is that I'm coming to New York too. NYU to be exact."

Kurt stared up at him, his mouth hanging open.

"Well, now he does," Sebastian amended a small smile on his face. "Maybe this song will help him understand why I decided on New York, and what I want to happen there."

Sebastian began to strum his guitar, leaning forward to sing into the microphone.

I was perched outside in the pouring rain
Trying to make myself a sail
Then I'll float to you, my darlin'
With the evening on my tail
Although it's not the most honest means of travel
It gets me there nonetheless
I'm a heartless man at worst, babe
And a helpless one at best

It was the second Kurt understood what the lyrics meant that he decided that a more perfect song had never, could never, be created that better described Sebastian, what he meant to Kurt, and apparently, what Kurt meant to Sebastian.

Darling I'll bathe your skin
I'll even wash your clothes
Just give me some candy, before you go
Oh Darling, I'll kiss your eyes
And lay down on your rug
Just give me some candy
After my hug

Kurt didn't understand what he should've done. Should he get up, stay silent? Sebastian continued to sing, and Kurt sat, mesmerized, the thoughts in his head tumbling faster and faster, his eyelashes wet with tears.

Oh, I'm often false explaining
but to him it all plays out the same
and although I'm left defeated
It gets held against my name
I know you've got plenty to offer, baby
but I guess I've taken quite enough
I'm some stain on your bedsheet
You're my diamond in the rough

Kurt sat immobilized, listening to Sebastian sing, his eyes meeting Sebastian's, his gaze unwavering as he continued to sing.

I'll be waiting for you
All the angels and their halos
All they do is keep me waiting and waiting

Sebastian finished singing, and with a last strum on his guitar, the few people at the bookstore burst out in applause, cheering as Sebastian gave them a small smile before jumping off the stage and walking towards Kurt where he sat at the back of the room. Before he reached him, Kurt got up to walk to the side of the bookstore, behind a bookshelf were he waited for Sebastian.

As Sebastian neared him, Kurt gave him a small smile. Pulling Sebastian closer, Kurt stood with his palms pressed flat against Sebastian's chest, his forehead pressed against Sebastian's.

"I'm sorry I kept you waiting," Kurt murmured, his breath mingling with Sebastian's, as he watched Sebastian's eyes flutter closed.

"It's fine," Sebastian said.

Kurt leaned forward and pressed his lips against Sebastian's in a chaste, dry kiss, his eyelashes fluttering against Sebastian's cheeks. Sebastian pressed in harder, bringing his hands to wrap around Kurt's waist, pulling him even closer. Kurt could taste the smoke and coffee on Sebastian's tongue, and he sighed into the kiss.

Pulling apart, he stood with their foreheads pressed together once again.

"God, I love you," Sebastian sighed, pressing a kiss to the side of Kurt's mouth.

"I love you," Kurt replied.

"Not I love you too?" Sebastian said.

"That sounds like I'm conveying my love as a response," Kurt whispered. "When really, it's a declaration."

Sebastian chuckled. "You're something else, Kurt Hummel."

"As are you, 'Bastian," Kurt said, before pulling Sebastian in for another kiss.