Only the Ring Finger Knows - Volume 1: The Lonely Ring Finger (Yaoi Novel)

It's the ultimate expression of love to wear matching rings with your significant other, showing the world that you are a couple. High school student, Wataru Fujii, also wears one even though he is single. When he accidentally switches rings with a popular and handsome senior, Yuichi Kazuki, they discover that their rings pair up! Since that moment, Kazuki - who is known for being kind to all - becomes strangely harsh to Wataru. They alternate between hot and cold, as in between clashes they begin to sort their feelings for one another. Are Wataru and Kazuki the worst of enemies or are they actually soulmates?