*This post may content spoilers, these are my personal thoughts only, read at your own risk.
A love story of fake incest (?)
At the start, the male character’s family was only responsible to raise the female character until she gets married. But slowly when they get along, they started to have feelings, and they see the female character as one of their family member.
Especially when the male character (also known as big brother) started to get along with the female character, he turns out to be a mad sister-con! Sometimes he’s afraid that the female character gets bullied, so he would stand out and act like a righteous brother.
Because there’s no female elder in their family, there’s a funny scene where the female character got her first period (I better not spoil any further). He scares that the female character started to date at high school times would affect her studies or get taken advantage. He notices that the female character doesn’t follow his plan and changed her major, and scared that the female character not get used to live in the university’s dorm.
Most of all, because he is used to raise up his little brothers, so he doesn’t know how to raise a little girl! The process of raising the female character is quite lovely.
The female character doesn’t have any strong personality, she had never get along with the male character’s family in the past, and because of that she wanted to make up everything this time. Especially when she realized how stupid is she in the past is quite heart aching.
The story goes along when the male character slowly realized his feelings towards her but couldn’t face his feelings properly.
When the “big brother” image of the male character in her heart has changed, everything is not the same for her anymore.