Invisible Cherry Bomb Glitch
The Invisible Cherry Bomb Glitch (aka ICB) is a state glitch with various effects, triggered by queuing up a day-night transition just as Ammy jumps into an activated Mermaid Spring and warps away. When the load finishes, all demon scrolls and devil gates will have disappeared, Ammy will not have the option to talk with NPC's (though their dialogue can still be triggered by tackling them), and Cherry Bombs will be invisible and never explode (until the glitch is cancelled).
Time-of-day still passes, and if a day-night transition occurs while ICB is active (either naturally or via Sunrise/Crescent), it will be cancelled. As an exception, ICB won't be cancelled by a day-night change if the normal transition cutscene doesn't play, such as when blooming guardian saplings. ICB is not normally cancelled by map transitions. For unknown reasons, entering Ryoshima Coast at all will cancel ICB. It can still be activated from the Ryoshima spring when warping to other maps.
Boss fights can still be started and work normally in ICB. If a non-boss fight is triggered via a cutscene (e.g. the Poltergeist fight in Catcall Tower), the game will softlock on the last scroll transition before the fight begins.
If one activates ICB, then warps to North Ryoshima before killing the Water Dragon, Ammy will instantly get stuck in an infinite loop of getting caught and eaten by the Water Dragon. This is a softlock. See https://youtu.be/nge3v87WtUA.
ICB can be transferred across saves by dying, then choosing the load option. This makes it possible to bring this state to any point in the game.
Because there are many possible interactions with ICB, more research into this glitch is greatly needed. For example, DriftingPancake has reported once obtaining Walking While Talking in Shinshu, which is believed to be related to ICB, but hasn't since been replicated. With currently known information however, it has no uses.
See this video for a general demonstration of ICB: https://youtu.be/R1eECciKllI