This is me reading way too much into the picture they took in ch.155. It pretty much got away from me.
Hilda stared at the picture they had taken at the airport before they had departed. She wasn't sure how she felt about it. She and Oga looked rather... cozy next to each other as Furuichi bemoaned furiously.
"—hate you so much!" he was yelling. Oga was ignoring him, playing his PS2. Furuichi wasn't exactly wrong, but he was making a bigger fuss of things. They weren't even touching in the picture. They were merely sitting next to each other. They also happened to look very comfortably close to one another, just shy of contact save for Oga's hand which was just brushing her arm.
"Quiet. Master needs his nap soon. Get out," Hilda ordered. Looking like a kicked puppy, Furuichi did as he was told.
"I thought he was going to be playing with those weird kids downstairs with my mom watching them," Oga questioned.
"The fool was getting on my nerves. What does it matter how we were sitting in a picture," Hilda said choosing to remain oblivious. Oga pressed pause and stood up.
"What is he bitching about anyway?" he muttered grabbing the picture. He stared at it for a second before his eyebrows went up.
"What?" Hilda asked, curious as to what he saw between them in the picture.
"Alaindelon is one creepy ass fucker," Oga stated, disturbed by his appearance under their seats.
Hilda's face fell imperceptibly, feeling foolish for expecting anything less. Oga, despite his appearance, wasn't the typical delinquent. There was a reason Be'el had chosen him. She'd seen glimpses of them and being a hormone driven teenager wasn't one of the reasons.
"Hey... we look pretty cool," Oga added. It such an odd comment that Hilda openly stared at him. "I mean, compared to everyone else, we look bad ass." He looked at her and there was something akin to amusement in his eyes. Hilda didn't understand and stood to take another look at them.
"Considering the company we keep, it is not all surprising," Hilda cautiously agreed. Suddenly, she realized they were close again. Ever since her amnesia, their contact was no longer innocent. She had ignored it of course, but at the moment she couldn't because they were so close.Then, Oga closed the distance further.
He kissed her.
Hilda literally gaped when he pulled away.
"You suck at this," he mentioned, as he closed her jaw for her.
"What is the meaning of this?" Hilda meant to yell, truly she did, but it came out as a whisper. At least she managed to glare.
"Who knows?" he answered with a shrug. Outraged, Hilda tried to punch him, but he caught her fist. She was glad to see that he winced at the strength behind her punch. He grabbed her wrists before she could attack him further. He did it with that uninterested look he normally had, as if her reaction had been predictable, and it infuriated her further.
"For a demon you're pretty modest," Oga said. It was like he was saying things to piss her off even more. In fact, she knew he was trying to get a rise out of her. So instead of flying off the handle, Hilda took a deep breath and let it out slowly.
"Let go," she commanded. Oga watched, his eyes eerily focused on her. Not backing down, Oga tangled their hands together. Hilda blinked down at the odd move.
"You can't be that oblivious," he stated, pulling her closer. Their foreheads touched, the contact making Hilda's heart pound. "This is all your fault for getting captured." He frowned, licking his lips.
"Explain yourself," Hilda muttered, her eyes flickering to the movement. They were so close it was distracting.
"If you hadn't... left, I wouldn't have realized how... important you are. In my—life," he grumbled reluctantly. Hilda lifted her stare from his mouth to his eyes and found that he meant what he said, however awkwardly he said it. Throwing caution to the wind, Hilda closed the distance further, closing her eyes as their lips met once more.
When she had lost her memories, she had imagined kissing Oga so many times it was pathetic—especially since she wondered about a lot more than just kissing. Thinking you had a baby with a person had that effect. Hilda had imagined he was delicate with her, that he hadn't been a man of many words, that he expressed his feelings through touch. It was sickening.
Except it wasn't this picture perfect fairy tale she had once naively imagined and she berated herself for unconsciously clinging to the idea. The kiss was not without it's awkwardness, his lips chapped and caught by surprise and not nearly as confident as before. Vulnerable, almost. The thought made her feel all the better. Hilda began to pull away, satisfied by her dominance, but Oga followed her, his hand going to the back of her neck to deepen the kiss, while the other went to her waist where he squeezed, it feeling painfully good. Hilda's hands fisted on his shirt, reciprocating his aggressiveness.
Finally, they pulled away breathing heavily. Trying to compose herself—there was a blush threatening to break out on her cheeks—Hilda glared at Oga.
"Don't try to pin the blame on me, fool. It's your fault for trying to play the hero."
"What do you mean trying, you ungrateful bitch? I saved you didn't I?" he yelled, glaring back. It was like they were back to normal again, save for the fact that they were so close and still clinging to one another. Slowly, as they continued to argue, they pulled away.
Later, when they were putting Baby Be'el to sleep, Oga said something stupid, Hilda hit him, and he pulled her to his bed so they could all sleep together.