This occurred in Brevard, FL. The complaint was lodged by a member of the community. From the article:

A person in the district challenged the book’s inclusion in the schools’ libraries on the grounds that “sexual orientation should not be encouraged, suggested, or implanted” in the youth.

…

The complaint also included concerns children would be “exposed to age-inappropriate, obscene, explicit content” and that there was “no value in making homosexual books available at school.” The book is rated for T for Teens.

The most insane part of this to me is that the chair of the school board also took aim at the right to left reading direction of the series (you know, like every other manga in existence) as well as it including a romantic relationship (like the vast majority of fiction):

Board Chair Megan Wright objected to the book’s content due to its focus on a romantic relationship, as well as the Japanese reading format of reading the book from right-to-left.