Tensai Expains it all. Otoko no ko "traps" are not boys or men.

Notes:

A frame from episode 2 of Nanana's buried treasure where a character Tensai Ikkyū explains that Daruku is not a boy.

Nanana's Buried treasure is unique in that it tried in a non overbearingly PC way to explain to people what an otoko no ko is. While no part of that word or what she says means he (see video) the translation "He's a trap" says it using the vernacular of western anime fans, many of whom, it seems, see folks like Daruku exclusively in terms of their own perception, gender norms and sexuality. While clearly Japanese Otaku do not see it that way.