It was strange how easily Nagisa became obsessed with things. It happens so quickly and effortlessly...It worried Rei to no end.

The blue haired teen never understood it. Every few weeks or so, Nagisa would latch onto something- Maybe an idea, a habit, an activity, sometimes even a person- And become completely and utterly obsessed with it. Rei just could not for the life of him figure out how these phases started. Nagisa's mind was an outright mystery. Even attempting to comprehend any piece of it always gave Rei a raging migraine and he could swear he was losing IQ by the second.

Some of them were normal, which Rei was thankful for. He could remember Nagisa's health kick phase- which was the shortest of them all, his American rap phase and even his couponing phase which ended with Nagisa having too many paper cuts to count. And then there were to more...Er, drastic ones that still relatively fell within the realm of normality, like when he decided to wear nothing but pink clothing for a whole three weeks. Rei had never been so embarrassed in his life.

Okay, so maybe it wasn't exactly normal to have so many pink items of clothing.

It was definitely unusual, but it didn't even compare to the more bizarre things the blonde had gotten obsessed with. Rei didn't think it was even possible to get more outlandish than pink swimsuits and pink school uniforms, but Nagisa had a habit of proving him wrong. There was the time he refused to take regular showers for two weeks straight, opting for a bubble bath every night instead. There was this short lived attempt to only eat foods that started with N. And then there was that baffling phase where Nagisa had refused to sleep in his room for almost a month, instead setting up a sleeping bag on the living room couch, the bathroom floor, and, on one memorable occasion, the dining room table.

Rei had no words when he found his classmate dozing off in his sleeping bag on the kitchen counter.

But...This new obsession was the most absurd one yet.

Nagisa's new obsession was kissing Rei when he was least expecting it.

The first time it happened, they had just finished swimming practice for the day. They were on the train home, Nagisa rambling on about something that happened in one of his classes while Rei continued to ignore the blonde and finish his book. The train came to a halt at Nagisa's stop and his classmate waved goodbye. Before he stepped off the train, he had leaned over and pressed his lips against Rei's. It was just a peck, so quick and light that Rei wasn't sure what had just occurred.

"W-What was that?" He had managed to stutter out through the initial shock.

Nagisa rolled his eyes. "It was a kiss, dummy." He'd shrugged and walked away as if nothing out of the ordinary had happened. If only that was the case.

Rei dismissed the event, distracting himself with some homework. He couldn't deny the blush that burned his cheeks every time the thought came to mind though. It was weird, but then again, it was Nagisa he was dealing with here. He was always doing insane things and coming up with irrational ideas. Rei discovered that if he ignored them, the antics usually stopped.

The second time it happened was at the sports shop, just four days later. Rei was shopping for a new swimsuit and he had stumbled across one that caught his interest, picking it out off the rack and examining it. When he turned around to head to the dressing room, Nagisa was right behind him. Before Rei had time to do anything but let out a surprised gasp, Nagisa had kissed him swiftly and sprinted off down the aisle, disappearing around the corner, giggling left in his wake.

"Nagisa, what the hell-?!" Rei had called after him. He swallowed the rest of his choice words and obscenities, focusing on ignoring the curious looks the other customers were giving him. He shook his head, fighting down the urge to blush.

Just ignore it, Rei. He reminded himself before running over to strangle the blonde in public. He's just looking for attention, just trying to annoy you. If you ignore it, he'll stop.

And of course, Nagisa didn't stop.

The third time it happened was the final straw for Rei. About a week after the shopping incident, they'd been practicing, Haruka and Makoto doing some laps, while Gou cheered them on from her post. Rei and Nagisa stood off to the side, drying off and watching their teammates.

"Good job, Haruka-sempai and Makoto-sempai! This is your best time yet!" Gou encouraged.

"Hey, Rei-chan?" Nagisa asked and he'd shuffled a little closer to Rei, poking his arm lightly. The blue haired teen turned toward his classmate, an eyebrow raised in question.

"What is it?"

Nagisa had given him a little smirk and, before Rei could stop him, planted another gentle kiss on his lips. Rei almost lost it right then and there.

"N-Nagisa! What the hell?! Why did you do that?!" Rei had shoved him away, blushing furiously. The blonde shrugged, grinning that excited grin of his.

"It was just too tempting." He smiled to the others and both Makoto and Gou cracked up with laughter. Haruka rolled his eyes, going back to his swimming.

At that moment, Rei wanted to jump into that pool and drown. But, he knew if he made a scene he'd be admitting defeat to Nagisa. And he was going to let hell freeze over before that happened. So, he'd finished practice as best he could, despite the teasing Nagisa and Gou forced him through.

It was that night that he decided that he had to put a stop to this obsession.

He was pretty confident he had this particular phase figured out, especially after that last episode. Nagisa thought it was great entertainment to see Rei get flustered and embarrassed. And it seems that blonde had finally found a way to do it that worked out perfectly. All Rei had to do was wait for the next time Nagisa decided to put his little experiment into effect and make sure he didn't resist. And then he would see just how bewildered he could get Nagisa.

Then we'll see who the real winner is.

The opportunity came along the very next day. Rei was on the train, reading another book, when Nagisa boarded. He yawned as he took his position next to Rei, leaning up against one of the bars.

"Morning, Rei-chan." He murmured tiredly.

"Morning." Rei responded. He was instantly aware of his classmate's movements, listening to his breathing and the way his voice wavered when he explained how his night went and why he was so drained this morning. Not once did he look up from his book, after all, he wanted to seem as unsuspecting as possible. Finally, Nagisa fell silent. Rei felt his breath hitch in his throat.

"Rei-chan?" He whispered.

Rei turned to him, trying to seem casual about the whole thing. "What do you want-?"

And Nagisa's lips were on his again, warm and smooth.

This time, Rei was prepared. Before the blonde could pull away, Rei grasped his hips, holding him still and pulling him deeper into the kiss. Nagisa's lips parted to let out a surprised yelp and Rei could taste him on his tongue. He tasted...Sweet. He used the opportunity to press his body up against Nagisa's, pinning him to the wall of the train. It surprised him that it took so long for Nagisa to give in, but what shocked him more was the moan he managed to extract from the blonde. He had to admit, it gave him second thoughts about the whole obsession.

Maybe it wasn't so bad.

But, before he could decide, Nagisa flailed his arms about, attempting to push Rei off. When he finally succeeded, he gasped, looking over the blue haired teen. His eyes were wide and Rei grinned with success when he saw the blush that had spread across his cheeks. "W-What was that...Rei-chan?"

"It was a kiss, idiot." Rei shrugged. He smirked, placing a small peck on Nagisa's cheek and walked off the train at his stop. He could feel Nagisa's eyes on him as he left and he couldn't resist sneaking one last glance over his shoulder at his shocked expression. He knew Nagisa would recover eventually and come back for revenge ten times as bad as Rei's, but at the moment, he wasn't worried at all.

He was looking forward to it.

He was right. Maybe this obsession wasn't so bad after all.