It's pure Bart the way it happens.
Kon received tons of boxes of conversation hearts from the members of his fanclub, and brought them to the resort to share (and boast about his fangirls, of course).
Cassie left in a huff after taking half a dozen boxes with her. Cissie whacked Kon over the head with her bow before doing the same. Kon finally realized what was going on – though he thought it was Cissie who was upset with him not noticing her – and left to buy chocolates or roses or, "Something to get them not mad at me, man!"
Tim didn't think they sold a book called Romantic Clues for the Clueless. In any event, Kon wouldn't have taken the time to read it, so it wouldn't have done him any good.
All of which left him and Bart alone in the resort – Suzie was off…somewhere, and Red Tornado was at home with his wife and daughter – with several dozen boxes of conversation hearts.
Tim snuck one box from the pile and stuffed it into his belt for later. Conversation hearts were somewhat chalky and tasted about as much like plastic as candy, but they were like candy corn at Halloween, or candy canes at Christmas; the holiday just didn't seem right without them.
Robin had gotten halfway through the first case file he brought with him from Gotham before he realized that most of the boxes of candy were still there. Bart was in the room; there hadn't been the telltale swoosh of air of him leaving. Bart wasn't sick, or – Tim checked in the reflection on the computer monitor – asleep; those were the only times he wasn't hungry.
So why wasn't Bart eating the candy? Did he not like the taste?
"Bart?" Tim asked the uncommonly-still speedster. He pushed off from the console, letting momentum carry him until he'd almost past Bart, then sticking one foot out to stop his movement.
"Hey, Tim," Bart said. His smile was as bright as ever, but his words were shyer than Tim had ever heard them.
"What's up?" Tim asked, leaning forward and making his body language more open. He discreetly made a few brief movements that caused his cape to fall behind him, encouraging Bart to confide in him.
Bart's smile became wobbly, uncharacteristic hesitation seeping into every pore of his body as he held out one closed hand.
Curious, Tim held out his own hand, palm-up, accepting the unseen object. When Bart's hand opened and he placed his offering on Tim's hand, the Boy Wonder's breath drew in at the sight.
It was a bright pink conversation heart. Written on the front in blocky purple lettering were the words Be Mine.
Mind working at speeds approaching that of Bart's, Tim got shakily to his feet, and stepped closer to his friend, hand closing tightly around the candy. Once Bart's wide, hopeful eyes were focused on his, Tim opened his hand and mouth, placing the candy on his tongue.
Savoring the saccharine taste of the even sweeter words on his tongue, Tim then leaned over and pressed his lips to Bart's, sharing the candy with him. Bart's arms impulsively wrapped around him, and Robin couldn't help but hold his new…boyfriend…back.
From Bart's happy giggles as their tongues traded the rapidly melting heart back and forth, Tim knew his 'Yes' had been received loud and clear.