It was a ballpoint pen with quite an impact to it. It seems to be a hard-to-get item, since they're apparently handmade and can only be made when the things can be caught.
I've seen a lot of unexpectedly odd links to explain translations here on danbooru, but that...'souvenir pen' is something I could never have expected.
Killing a parasite is one thing, but to watch it slowly starve and die is a little bit different.
SHREEOOOM
Looked It Up Later
Kōchi Ryōma Airport...Thanks for all you did on this trip.What IS that!?I had a blast thanks to you.I'm glad you were thoroughly able to enjoy yourself.There's just one thing I regret...Oh? What's that?I forgot to buy an Anisakis ballpoint pen on the way back from Kure.Pardon!?'The heck is that!?See ya!Waaait!