Just a Rei and Kiku thing
Rei was laying in bed, staring at his adorable little daughter laying beside him. She just turned a year old a few days ago. Kaoru had come home for her birthday but then left the day after. It made Rei sad that he left so quickly but at least he came home for Kiku's birthday. She was clinging to the seal plushie he had gotten for her before she was even born, it was so cute to watch her cuddle with the plushie. He reached over and gently grabbed one of her hands, a goofy smile coming to his face when she gripped his thumb and looked over at him.
She cooed and smiled at him, she reminded Rei of when Ritsu was a baby. She had Kaoru's eyes though, instead of red like Rei's.
"Mama," she spoke while making grabby hands, which usually meant she wanted a hug. So he pulled her close and nuzzled her, earning a happy giggle from her.
"You know I'll never let anyone hurt you, right? Kaoru has told me of the dangers you'll be in, since you are a selkie like him. I'll kill anyone who would do you harm," he said as Kiku nuzzled him. She was babbling back, as if she were talking to him. Even though she probably didn't understand Rei's words.
It wasn't as if he were completely clueless. After all, Rei had stolen Kaoru's coat when they first met and kept him trapped here with him for years. If he hadn't, Kiku might not have been born at all, nor would they even be planning to have two more children in the future. And while that worked in Rei's favor, it left a sour taste in his mouth when he thought about the same happening to his precious daughter.
He held Kiku close as he sat up and then put her down in his lap. She stared up at him and tilted her head. "Mama?"
"It's nothing, my little seal. I should lay you down, my next meeting is going to start soon," he said, watching as a grumpy expression came onto Kiku's face.
"No. Stay," she said, making Rei laugh. Ritsu had told him that many times, but Kaoru had told him not to spoil her like he had done to Ritsu. So he picked her up and went over to the crib, laying her down. He had to look away when her eyes got all teary, he was weak to her sad face.
"Go to sleep, princess. When my meetings are over, I'll run a bath for you and you can play in the water," he said. Kiku already loved the water but Rei wouldn't let her go in the pool yet. Not without Kaoru, since he didn't know how to swim and wouldn't be able to help Kiku if something went wrong.
He heard her make a little 'hmph' and looked back in time to see her roll over, her back facing him. She was sulking, it was adorable. He gently patted her head.
"I love you," he told her, before stepping away and heading out of the room.