I think this and the parented images are part of the other story, with Rumia. Looks like Flan sends Boytoy here out on a shopping errand, and shoves a crystal down his throat to protect him. Then when he meets Rumia on the way she tries to chomp his head and the crystal repels her.
Don't worry about it, just open up!Nngah gwaughWhat... is this...
It's pulsing inside of my stomach...Eh?
It's the Devil's (Sister's) Fruit.
Of course you won't be able to swim any more so be careful.
As for its effect, that's as a surprise for when the time is right.