Yuhei Takashima had meticulously catalogued nearly 150,000 photographs of his exploits over a 27-year period in around 400 separate albums because he wanted "to keep the memories", Jiji Press and other media said.
Takashima, aged 64, told police he started paying for sex when he was dispatched to a Japanese school in Manila in 1988, Jiji said.
Thereafter, the former middle-school principal had been on three sex tours a year to the country, for a total of 65 visits, reports said.
During this time, he had sex with more than 12,000 women, who broadcaster NTV reported were aged between 14 and 70.
No report gave a breakdown of how long the tours were or how many women he slept with on each one, however it averages out at more than one a day every day of his life since his first visit.
Takashima told police that about 10 percent of the women were under 18 years old, Jiji said, citing unnamed police sources.
He was arrested for having sex with a girl in Manila last year believed to be 13 or 14, under powers police have to prosecute certain crimes committed abroad, Jiji said.
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