@Mimik age of consent in Japan is thirteen. So to the author, it's probably as normal as when we watch movies with an 18-year-old love interest. That and it's a cartoon set in a medieval fantasy world, so different morals too. Think Game of Thrones. It's a cartoon anyway so it doesn't matter anyway.
Deleted the chapters? Guess I'm dropping or just going to read these on another (less ethical) site, I'm following over 50+ manga/manwha. Even for scanalters I donate to, I'm not going to use their crappy sites when the alternatives can be used for easy bookmarking.