The Night Beyond the Tricornered Window

さんかく窓の外側は夜 (Sankaku Mado no Sotogawa wa Yoru)

6.8(17,671)

MAL Score

Ranked #6127

Popularity #3466

Boys Love
Drama
Horror
Mystery
Supernatural
Adult Cast

Episodes: 12
Duration: 23 min per ep
Aired: Oct 3, 2021 to Dec 19, 2021
Status: Finished Airing

Synopsis

Kousuke Mikado has been able to see spirits since childhood, a gift that only leaves him frightened. Hoping to dull what he perceives, he hides behind a pair of glasses and keeps his life as ordinary as possible—until a chance encounter at the bookstore where he works draws the attention of Rihito Hiyakawa, an unconventional medium convinced their meeting was fated.

Pulled into Hiyakawa’s investigations despite himself, Mikado is promised that staying close will help him overcome his terror. As the two begin working side by side, they stumble upon a string of vicious curses that all lead back to a single name: “Erika Hiura.” With each case, the connection between that name, Mikado, and Hiyakawa grows harder to ignore.

Otaku Consensus

The Night Beyond the Tricornered Window lands as a divisive but distinctive supernatural mystery: its best material is the morally uncomfortable Mikado-Hiyakawa dynamic and the shift from casework into the Erika Hiura conspiracy. Reception settled in the middle range, reflected by a 6.76 MAL score and 64/100 AniList score, with the main criticism aimed at Zero-G’s restrained visuals, limited character acting, and uneven character development rather than the occult premise itself.

Why You Should Watch

Watch this if you want occult detective work built around adult discomfort rather than shounen power escalation. It scratches part of the same itch as xxxHOLiC’s client-based supernatural investigations and Mononoke’s psychological body-horror unease, but replaces their eccentric visual spectacle with a colder, more intimate push-pull between two men whose partnership is as unsettling as the hauntings. The Boys Love element is not framed as soft romance; it is tied to dependence, psychic vulnerability, control, and the question of whether protection can still feel invasive. Viewers drawn to urban ghosts, crime threads, conspiracies, and morally messy professionals will get more from it than anyone looking for kinetic exorcism battles or lavish horror animation.

Key Characters

K
Kousuke Mikado
Mikado is the show’s vulnerability engine: an adult protagonist whose psychic sensitivity turns fear, consent, and dependence into the real sources of tension.
R
Rihito Hiyakawa
Hiyakawa is the character fans debate most because his flexible morality makes him read simultaneously as protector, manipulator, and dangerously competent occult professional.
E
Erika Hiura
Erika Hiura gives the series its crime-conspiracy spine, functioning less like a one-off supernatural antagonist and more like the human name that keeps pulling separate cases into one pattern.

What Makes It Stand Out

1
Zero-G produced the 12-episode TV adaptation, with Daiji Iwanaga credited as chief director and Yoshitaka Yasuda serving as both director and character designer, concentrating the show’s visual identity under a small leadership core.
2
The series composition by Ayumi Sekine structures the anime less as pure episodic ghost hunting and more as a gradual convergence of urban hauntings, crime clues, and the Erika Hiura thread.
3
AniList’s tag profile is unusually revealing: Ghost at 92%, Primarily Adult Cast at 90%, Conspiracy at 88%, Crime at 87%, Detective at 76%, and Body Horror at 74% place it closer to occult procedural horror than conventional BL romance.
4
The Boys Love tag sits at 62% on AniList, which matches the anime’s reputation: the relationship tension is central, but it is filtered through supernatural dependence and psychological danger rather than domestic romance beats.
5
The most repeated visual critique is specific rather than vague: reviewers pointed to limited clothing variation, restrained facial expressions and body language, and plain scenery as the places where the adaptation felt underpowered.

Fun Facts & Trivia

Fun fact 1: The anime aired as a single cour from October 3, 2021 to December 19, 2021, finishing with 12 episodes.
Fun fact 2: Tomoko Yamashita is credited as the original creator, while the anime’s screenplay-level organization was handled by series composer Ayumi Sekine.
Fun fact 3: The production’s background and image pipeline lists Masazumi Matsumiya as art director, Mikiya Hiragi on art design, Akira Hashigami on color design, Tomomi Saitou as director of photography, and Masaki Utsunomiya on editing.
Fun fact 4: On MyAnimeList, the series sits at 6.76/10 from 17,671 votes, with a rank of #6127 and popularity of #3466, indicating a niche title with enough visibility to spark debate but not broad consensus acclaim.
Fun fact 5: AniList records 221 favourites for the anime, a modest but clear sign of a smaller committed audience around its ghost-detective premise and Mikado-Hiyakawa dynamic.