Well, on e-hentai solo male is also considered yaoi when the target audience is gay men, this is an odd one tho, it's hetero sex but the target audience is obviously gay men (everything else by the author is male only, the female has almost no details drawn, etc), so it kinda fits the e-hentai definition of "yaoi" (gay male target audience) but not what most people think "yaoi" is (sexual contact between two men), quite the conundrum