Inu mo Kuwanai

From Yaoi Is Life: Utsugi is an investigator working for a detective agency. When he's asked to track the wife of a college professor, Yamashiro, he discovers that she's cheating on him with another professor from the same university named Okuzono Shuji. But this isn't the first time it's happened. Okuzono has stolen away the women Yamashiro loves countless times before. These intellectuals are embroiled in a twisted and convoluted relationship, and now this young investigator finds himself thrown into the mix.