The central character of this shoujo romcom has stated canonically that they don't want to live as a boy or a girl, just as themselves.
The protagonist has canonically stated she doesn't have strong feelings about her gender or how others perceive her.
The protag/author is canonically x-gender, a Japanese term for non-binary. They also meet another x-gender side character at one point. They also have an acquaintance who identifies specifically as nonbinary.
The main love interest, Arima Yuu, struggles with gender issues throughout the story and ends up finding acceptance and hope for the future outside the binary. Canonically says they're neither male nor female.
The MC of this oneshot manga is canonically bigender and their romantic partner is canonically agender.
One of the 2 main characters is canonically nonbinary and uses they/them pronouns.
The love interest slash second most major character in the story is canonically nonbinary.
There's a canonically bigender character who is first properly introduced in chapter 3 and gets their personal story explored in chapter 4. Chapter 8 also features a canonically graygender character, and chapter 10 introduces an agender character.
One of the side characters is canonically outside the gender binary, but without any fixed identity or label - they identify essentially as "whatever you think I am, that's what I'll be to you."
One of the side characters, Juno, is canonically nonbinary/agender.
Senpai wa Otokonoko