whit this picture rider of black look complet like a woman, theres no bulge of signs of male genitals
Trap artists do that a lot. They will draw a girl and just say "its a boy". At this point I deny their reality and subsitute my own. If it's cute its fine. Once I see a bulge then it's all aboard the nope train.
IIRC regarding D'eon, isn't there something about how D'eon changes to a specific gender based on their Master's preference or something?
D'eon's Self-Suggestion skill lets him genderswap at will. So he can become a she if his master would prefer it and he decides to go along with it, yeah. He can also troll his master by staying as a girl then switching when it comes time for mana transfer if he would prefer.
It's too bad that D'eon's character is just so boring though.