The 61-year-old woman allegedly attacked her partner after learning of his affair, battering him repeatedly about the face and head with the mug at their home southwest of Tokyo on Sunday afternoon, the Asahi Shimbun and other media reported.
Yasuo Hirose, a 70-year-old honorary professor with Yokohama National University, was taken to hospital but later confirmed dead.
“He had an affair with a woman I hate,” Emiko Hirose told police, according to the reports. “I went mad and hit him more than 10 times with a cup.”
The wife has been arrested on suspicion of attempted murder, reports said. Immediate confirmation was not available.