I wish they put this up in the summary section.
I was so frustrated with the summary posted because it implies a whole different story where a woman might be involved. It prompted me to find this instead.
The uploaders posted a comment above (Dec 10), so I asked if it's possible for them to edit the summary and told them that someone kindly provided a good summary below in the comments section. I only checked now and it seems they used your summary! It's corrected now.
A better summary
With their parents' divorce, Doyeon and Eunha, who had become a family through their parents' remarriage, turned back into strangers.
After several years, they meet again, and Eunha had become obsessed with Doyeon. While Doyeon finds this clinginess from his brother burdensome... what he dislikes even more is realizing that his feelings towards Eunha are not simply 'brotherly love...'