The couple from eastern China took a spare toilet seat from underneath their bed after they stayed at a hotel in Nagoya on Monday, Yong Pai reported, an online news service operated by the Ningbo Daily.
After their tour group had left, the hotel found out about the missing seat and contacted the travel agency to demand it be returned, a tour guide with the group was quoted as saying.
The toilet seat was sent back to the hotel after the group arrived at Mount Fuji, the guide said.
The couple took the toilet seat because they thought it was left by other guests who had stayed in the same room, they said in an apology published online.
“I offer my sincere apology and regrets,” the statement said. “I hope the hotel and the local travel agency can treat this with leniency. I promise this improper behaviour won’t happen again.”
The couple has promised to apologise again when they stay at a hotel in the same chain on the last day of their trip, according to the report.
The Ningbo Tourism Bureau confirmed the couple had travelled from the city in Zhejiang province to Japan this week.
The wife works as a manager at a commercial bank in Taizhou, according to the report.