There are many trends that become signature anime elements, both for better and for worse. “Fan service” is a concept that refers to gratuitous visuals of an anime’s female characters as a way to create enthusiasm and anticipation. Fan service can be a popular marketing tactic that gets audiences to tune into an anime in the first place. However, fan service can also invade its way into series and awkwardly stand out.
Source：https://www.cbr.com/fan-service-anime-with-plot/
