As you might have guessed, what prevents me from giving this the perfect score is the age of the protagonist and her main love interest. Mao is a 17 year old high school student, while Hiro is a 24 year old office worker. And of course, they start getting romantic with one another. Essentially, Hiro groomed the shit out of her. Furthermore, they've had this sibling dynamic since they were children. This relationship switching into romantic one is also ethically questionable.
The bitter truth is that this relationship is weird, to say the very least. Especially with one of the main characters being an S-tier, major league professional child groomer. Even with these downsides, Taiyou no Ie is still a unique manga with banger romance sequences, complex relationships, and many heartwarming stories to share. If you can accept the fact that this is a work of fiction and bear with classic Japanese media being classic Japanese media (forbidden/taboo relationships, pedophilia and incest), then you should give it a try.
I give this manga a 9/10.
