Gunma police on Tuesday arrested a man for allegedly throwing sulfuric acid at a 23-year-old woman last week in Takasaki, Gunma Prefecture, causing minor injuries.
Noriaki Kitamura, 30, unemployed, has denied the charge.
The police are also investigating his possible involvement in three similar incidents.
Four women reported injuries after apparently having sulfuric acid splashed on them in Takasaki on Thursday and Monday. They all suffered burns to their legs, and while their injuries were relatively minor, the acid burned through their clothes, the Gunma Prefectural Police said.
On Monday, the police released surveillance camera images of a man apparently acting in a suspicious manner where the incidents took place. He was wearing a black jacket and beige pants, and he carried a black bag.
According to the police, at around 6 p.m. Thursday, a 44-year-old part-time worker from Shibata, Niigata Prefecture, felt pain in her right calf while shopping at a store in the building adjacent to JR Takasaki Station. The police found traces of sulfuric acid on the woman, whose cardigan and bag were also found to be damaged.
About an hour later, at a shopping center about 4 km southeast of the station building, a 23-year-old office worker from Fujioka, Gunma Prefecture, reported feeling pain in her left ankle.
At the shopping center the same day, a 21-year-old college student from Tamamura, Gunma Prefecture, suffered burns to her left foot, and parts of her sweater and stockings were found to have dissolved.
Then at around 6 p.m. Monday, a 34-year-old office worker from Shibukawa, Gunma Prefecture, suffered burns on her right foot while shopping at a convenience store at JR Takasaki Station. Her stockings were also damaged, the police said.