Mitsuki's Rainy Day

During a downpour, Mitsuki follows his cat Mikazuki to a bleeding man collapsed in an alley and takes him home for first aid. The stranger introduces himself as Samidare and finds it curious that Mitsuki never asks how he was hurt, though Mitsuki simply says he does not mind unless Samidare wants him to inquire. Once healed, Samidare explains he came to see his younger sister, who works at a large Konoha firm, and buys Mikazuki a new bell collar in thanks. Soon after, Boruto and Sarada summon Mitsuki for a guard mission: Kōtarō wants Team 7 to shield the head of the Kaneki Corporation, the probable next victim of a killer who strikes only when it rains.

Every victim ties back to an accident years earlier at a Kaneki chemical plant, yet the executive claims to recall nothing and waves off protection. Team 7 guards him covertly, and when the rain comes a masked intruder drops the bodyguards without a blow before Mitsuki drives him into a river. Studying the plant records, Mitsuki notices a detail, and after Kaneki is abducted on a dry day, he exposes Samidare as the Rain Killer standing over the grave of his sister Mikazuki Amaashi, whose reputation Kaneki destroyed to protect his own profits. Samidare admits he began only seeking the truth but turned to murder when the others mocked the dead. A rain-fed duel of Water Release against Mitsuki's Lightning Release ends with Samidare turning his jutsu on himself.

This is a Boruto anime original episode with no arc assignment listed. It aired in Japan on July 5, 2020, and in English on November 23, 2021. In the closing scene the plant investigation reopens and Mitsuki visits the comatose Samidare, fastening the cat collar he bought around his wrist. The opening theme is Starting and Growing and the ending theme is Maybe I.