Yuri drowned while rescuing a young teenager in Japan and is reborn as the son of Rook, a rancher of riding birds and kingeagles (giant eagles for riding). We follow his first twelve years, starting with his birth and ending at him entering the Academy, focussing on a couple of important events in his life which does involve the occasional bit of knowledge of his previous life. We also learn he is not a human, but they live in a world that is remarkable similar to Earth geographically, astronomically and biologically (except for the birds and Yuri's own race that is).
Personally, I like the slow-paced slice-of-life story and world building even though it feels more like a traditional no-magic fantasy YA story than an isekai. The world has an intriguing mystery behind it, and I like that it is both the same to RL medieval Europe and yet different. I would have given it 4 stars where it not for the MC. The fact that he thinks he is an adult and act like a kid is fine even if a bit exasperating at times. It makes sense in a way. I dislike his passiveness though, for a supposed intelligent person he lacks curiosity, and he is awfully quick to jump to conclusions based on his Japanese knowledge despite being proven wrong again and again. For example, early in the book he asks for an empty book for a diary, his father says books are really expensive, naming the price. He then wonders how many breads can be bought, but never asks and weeks later when actually buying the book he still has no idea on the value of money. And the story is filled with examples like this, and sometimes he even blames the adults for not telling him enough, again not seeming to learn from it at all.
Still, I enjoyed the book, and I am curious where things are going, but it is not the best of its genre.