Japanese doesn't have gendered pronouns. There is no "he is tall," or "she has red hair." It's instead replaced by "Opera-san is tall" & "that person has red hair." The speaker and/or translator doesn't have to intentionally be tricky to hide genders or imply no gender- that's just how the language is structured.
Suffixes aren't 100% either, as a -chan, while usually used for girls, can be used to show that the speaker is really affectionate towards the subject (see Azz-Azz's mom calling him Alice-chan). -kun can also be mixed: it usually refers to younger males, but can be used to refer to female subordinates in an workspace.
You usually have to wait until there's confirmation by the author with a firm "Person A is a boy," but I'm pretty sure Nishi is having fun not giving a direct answer.