Ryou's Parents are Foreign Spies.
After Episode 11a/ Chapter 13, what we know about Ryou's parent's "work" that puts the girl to Parental Abandonment
are as follows:
- They are posted outside of Japan.
- They are extremely vital positions, although Kirin's mom and Ryou herself differ on how important they are; at least they make or break a city.
- It's top-secret. Nobody is comfortable describing it, even when asked by a person as close as Kirin.
- No family breaks allowed. Ryou still remember how her mother looks, but they haven't been seeing her for a whole year in in-universe time.
- They think Ryou is enough of a Living MacGuffin to need a bodyguard. They even think Kirin needs a bodyguard.
It's hard to think of any other positions that fits these descriptions.
- Chapter 28 gives one more hint: Ryou's mom's workplace can have "serious explosions."
Ryou's grandmother was taken out as a soft target.
She knew that she didn't have much time left so she passed the apron onto Akira.
The grandmother portrait in Ryou's residence is secretly a Harry Potter-type image.
She's just really good at keeping poses static when the camera is pointed in that direction during the final episode.