Story 12: The Strongest Assassin is a stage in the "Story Mode" of Resident Evil 4: Mobile Edition, the iOS and Android adaptation of Resident Evil 4.
"Awaiting Leon as he arrives at the old water canal is the deadly assassin, Verdugo!
— Official description
This area is a recreation of Salazar Castle's Old aqueduct B. As this is a boss stage, the only enemy in this room is the Verdugo.
In terms of treasure items, the Crown Jewel is rewarded after defeating Verdugo, while a Velvet Blue can be found hanging on the wall of one of the rooms.
Luis' Memo 2 is found near the elevator, next to a First Aid Spray.