Something that appears when a person is connected through the heart and the body. During the first intercourse between two parties who fall for each other, they should have a red line like a thread connecting their pinky finger. In this method, there is a single person having the upper hand in the connection formed between the two parties. But maximum everyone had an only single partner throughout their life except some special cases.
The MC, Xia Dongyi has been connected to 3 girls.