Public indecency, including being naked outdoors and sex in the public is punishable by Japanese law. Showing off your genitals in say, a public park will land you in prison for no more than 6 months.
https://tachikawa.vbest.jp/columns/criminal/g_sex/775/
Before making a thread, try making better questions that doesn't sound like it came out of the mouth of a 12-year old that just recently became a weeaboo just because he watched N*ruto.