The Drainage Tower in the Land of Rain appeared on no public map.
It had been built during the Second Shinobi World War, originally to channel floodwater from the west into the Abandoned Mine.
After the war ended, the tower aboveground had been destroyed by explosives.
The underground pipes, however, had remained.
The coordinates Obito provided pointed to the deepest Diversion Chamber.
Konoha did not send shinobi directly across the border.
The Land of Rain still had not permitted armed Konoha personnel to enter, and leads concerning the Akatsuki were no justification for ignoring its borders.
Shikaku first submitted a pollution investigation request through the Land of Rivers' government offices.
Abnormal white fibers had indeed appeared in the river near the Drainage Tower, affecting two villages downstream.
The local liaison in the Land of Rain agreed to have two craftspeople from their own country enter the pipes, with the Land of Rivers supplying water quality records and Konoha receiving sealed samples only outside the border.
The local liaison had not authorized a military investigation on behalf of the entire Land of Rain.
The permit covered only repairing the waterways, identifying the source of the pollution, and removing dangerous objects near the entrance.
If they discovered armed personnel, living White Zetsu, or core Akatsuki facilities, the two craftspeople had to withdraw immediately.
Every question submitted by Konoha was also screened first by a Recorder from the Land of Rain.
Information concerning local residents' names, resistance organizations' routes, and former shelters could not be taken out of the country.
Black Zetsu's use of a small country's borders to hide his bases did not mean a great power could once again treat those borders as nonexistent in pursuit of him.
Nagasawa and other exiles from the Land of Rain also helped identify old