How to Get the Memento Lens?
The Memento Lens is an essential gadget for the Sacred Sakura Cleansing Ritual questline. You get it specifically from the Sacrificial Offering quest.
You'll have to interact with the giant Sky Kitsune statue and a Mysterious Statue. Next, you have to find three shadows and guide them to stand behind three kitsune statues nearby. Your following location is the Grand Narukami Shrine. You must talk to Inagi Hotomi to get the Memento Lens.
You first must find a small kitsune statue to use them. Use the lens and focus on the figure to “see something that wasn't there.” This gadget is crucial for some puzzles and Electroculi. Don't skip the questline because it unlocks many features of Inazuma. Without it, you'll be locked out of many chests and treasures.