You may take some convincing but the Meguro Parasitological Museum is well worth a visit.
Apparently, and not unsurprisingly, it is the only parasite museum in the world and has a large collection of the nasty critters preserved and exhibited. Indeed it pulls no punches for the squeamish and arrays an impressive display against you as soon as you walk in the door.
Upstairs the 8.8 metre long tape worm removed from the stomach of a 40 year old man is truly stomach churning.
The museum is free but is, unlike many other free museums, really nice. The display cabinets‘ glass is clean so your view of some extremely unpleasant looking (and large) helminths is unobstructed. There is a souvenir shop upstairs where you can even buy some sealed in plastic key rings or T-shirts bearing nematode portraits for that more conversational of presents.
Great place actually and, believe me, I never thought I would write that.