my dad actually didn't tell me about his cancer either, I don't think their parents meant it as garam interpreted it. it's understandable he reacted that way but parents simply act and think differently when it comes to their own children and making them worry about a person who is supposed to be their 'guardian' and someone who is basically indestructible. it's an interesting topic to take on in a manwha that's for sure, I hope they handle this well with his parents
From what I heard the guy he calls "dad" is apparently his step dad and his behavior towards Garam isn't the one of a caring parental figure, since he's the one who answered the phone he probably didn't care about wanting to shelter Garam. I get not wanting to worry them but acting all casual and dropping that she had a surgery just like that after keeping it quiet is just a big no.

We're finally in the fluffy phase ヾ(❀╹◡╹)ノ~
But also what the heck, like I get the idea of not wanting to worry him but how could they just say "well it's not like telling you would change something" to their son ffs. And also just answering like "hey your mom's surgery went well" after not telling him anything about said surgery...