Only the Ring Finger Knows: v. 3: Ring Finger Falls Silent (Yaoi Novel) by Sattour Kannagi
After all the studying he did for his exams, sacrificing time with his boyfriend Yuichi, Wataru gets a measly C-average on his summer prep test. Yuichi's college classmate Asaka offers to tutor him, and he eagerly accepts. Wataru finds Asaka's cool beauty and attitude strikingly similar to that of Yuichi's, and subconsciously becomes vulnerable to his advances. For the first time in their relationship, Yuichi becomes enraged. Will they be able to overcome this new obstacle?