I don't think this is the main story of the manga. There were 2 brothers and they live in the same house. The little brother openly confesses his love to his older brother but the older brother brushes him off. Then one night, the little brother wanted to head to the toilet to pee and walked past the older brother's room. He caught the older brother calling his name while masturbating and walked in to confront him. I forgot what happened next but somehow they started making out and the older brother took out a bunch of tools and said that he dyed the rope pink for him.

Chapter 7 of Sailor Danshi by Sakira

OMG I LOOKED AT THE MANGA AND STUFF AND DIDN'T NOTICE IT..
(because there were no synopsis on it) D:

THANK YOU SO MUCH! <3