Anime typically involves at least a small amount of fanservice, and this isn't always a bad thing. Fanservice is added to please the audience at a base level, and series like Neon Genesis Evangelion and Kill La Kill prove that fanservice can be thrown in — or even be a core part of an anime's plot — without taking away from its overall enjoyment. However, because much of fanservice is sexual in nature or at least suggestive, it's easy to go overboard and ruin a compelling story with uncomfortable or unnecessary additions.
Source：https://www.cbr.com/anime-with-a-lot-of-fanservice/
