Conan vs. Double Code Mystery Meitantei Conan : Season 17 Episode 20

Conan solves the case and allows the person Sherry suspects to be a black organization member to stay at Shinichi's House. There is a rain of paper planes which people have labelled a prank. Afterwards Conan finds out the planes have morose code with the words S.O.S. Ran with Sonoko tagging along, is on her monthly cleaning trip to Shinichi's house and finds Okiya Sabura. They show the plane to Okiya and he tells them it's an S.O.S