Sankaku no Kyori wa Kagirinai Zero

is a Japanese light novel series written by Saginomiya Misaki, with illustrations by Hiten. The series began publication on May 10, 2018 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
In order to fit in at school, Yano Shiki adopts various personas to please the people he interacts with. One day, while he is at his desk, classmate Minase Akiha—a beautiful new transfer student—comments on the book he is reading. This particular book does not suit his character, so he begins making up excuses to conceal his true tastes, when Akiha suddenly dashes out of the room.

The following day, Yano observes Akiha acting noticeably different. After he confronts her, she reveals that she suffers from a split personality disorder, a case similar—but not identical—to himself. Declaring themselves comrades, the two decide to support each other until the day comes when they can reveal their true selves.

Manga Volumes
The manga adaptation of the light novel: with art by Kasumi Morino. It was serialised in KADOKAWA's Comic Alive and released under their MF Comics Alive Series imprint from October 2019.