Ryoma would be a protective father. His quiet nature would make him seem like a bit of an enigma to the baby at first, but as the baby grows, Ryoma would open up more. He'd be a great role model for the baby in terms of discipline and focus. Sakuno would be warm and bubbly. She'd be the one to create a happy and harmonious home environment for the baby. Her kindness would be something the baby would always be able to rely on, and she'd be the heart of the family.
In this fanfiction, Ryoma would still have his competitive streak, but it would be channeled into making sure his baby has the best opportunities in life, especially in the world of tennis. He'd be a bit of a strict father in that regard. Sakuno, on the other hand, would be the soft-hearted one. She'd be the one to encourage the baby to explore different things, not just tennis. She'd be extremely empathetic and understanding, and her nurturing nature would be on full display.
Ryoma would be calm and collected as always, but with a newfound sense of responsibility. He'd be more cautious and less impulsive. Sakuno would be very gentle and motherly. She'd be full of love and patience, always there to comfort the baby. Ryoma might be a bit more reserved in showing his emotions towards the baby in public, but in private, he'd be very affectionate.