So... is Haiyore! Nyaruko-san finished or not?
NO, it is not finished.
Why?
The anime finished after the manga:
Anime finished: June 19, 2015
Manga finished: March 17, 2014
... But MangaUpdates contains information about the anime adaptation and indicates that it is incomplete.
Watching Order (by release date)
Here you have all the anime relations we detected ordered by release date, so you can see the reason for this status in context and also use it as watching order.
The mangas and the non-core contents are excluded by default, but you can enable them by clicking the buttons below:
Haiyore! Nyaruko-san
Nyaruko: Crawling With Love!
Anime - Base
Release date: April 10, 2012
Haiyore! Nyaruko-san W
Nyaruko: Crawling With Love! Second Season
Anime - Sequel
Release date: April 08, 2013
Haiyore! Nyaruko-san F
這いよれ！ニャル子さんF
Anime - Sequel
Release date: June 19, 2015
Synopsis
Mahiro Yasaka, a typical high schooler, finds his life turned upside down when he's targeted by a dangerous alien creature.
He's rescued by Nyaruko, an alien who identifies herself as the Lovecraftian deity Nyarlathotep and an agent from the Space Defense Agency.
Nyaruko falls head-over-heels for Mahiro and insists on moving in with him, much to his dismay.
Soon, they're joined by other eccentric Lovecraftian entities: Cthuko, who has a strong affection for Nyaruko, and Hasuta, who has a somewhat ambiguous gender.
Together, this unusual group must protect Mahiro and Earth from various alien threats, while simultaneously making Mahiro's everyday life chaotic and challenging.