Okay, this review may sound strange, but I cannot let this point slide as a Lab Technologist. (I'll leave the normal review of the series to the others)
Here we go,
In one scene, Sun needs a massive blood transfusion, and they bring to him all the blood he has been donating as a backup in case Sky needs since they both share the same rare blood group.
They said that Sun has been donating blood every three months. A person can only donate 470ml (two blood units) at a time, and the blood units are only stored for 42 days if we do not freeze them. Frozen blood can be stored for ten years, but freezing blood is a poor way of storing it because there is a high chance that most of the RBCs will be hemolyzed upon thawing, thus losing the blood's value. So generally speaking, blood is stored in the refrigerator for up to 42 days.
While I can understand that Sun is donating his blood to keep some blood available in case Sky needs it.
In that particular scene, the stored blood wasn't that much in the first place, as Sky's father led his son to believe. The blood couldn't be more than 2 or 3 units. I think they should've shown Sky donating his blood to save Sun, instead.
Anyway, I just wanted to clear this point out.