At Ryokuyo High School, rings that showcase one's relationship status are the latest trend. Matching rings on the left ring finger signify a committed relationship, while a ring on the right middle finger shows that one is single. When Wataru Fujii runs into super popular upperclassman Yuichi Kazuki in the restroom, they accidentally swap their shockingly identical rings. Wataru does not realize it until Yuichi comes to his classroom to correct the error. Rumors are now swirling about the two boys wearing matching rings, but Wataru is more troubled by the way Yuichi treats him—despite Yuichi's princely reputation, he shows nothing but disdain for Wataru. As circumstances keep bringing them together, Wataru starts to wonder what Yuichi really thinks about him and the rings they share. [Written by MAL Rewrite]

Sono Yubi dake ga Shitteiru was published in English as Only the Ring Finger Knows by Digital Manga Publishing on August 1, 2004.