probably because of omegaverse shenanigans- aka heat and the lack of control over instincts
why didnt i ever think of that! ykw this made me think like what if
yuuma went into heat like accidentally went into heat, ren couldn't control himself and yk they fucked.
ren liked yuuya but since he accidentally went outta control with yuuma, he had to give birth to sana.
he felt guilty for both ren and yuuya so he left sana and ren alone. like why tf am i making my own plot
well do u want spoilers or...
Yes badly
spoilers i got from comments below
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about the pregnancy u guessed it right except that it wasn't accidental on the twin's side, he purposely timed his meeting with his heat cycle so ml would lose control. as for the reason, im not sure which one is the truth. some say bcs he knows ren & yuuya like each other and wanna help them have a kid, some say yuuma had feelings for ren too
Trash twin either way
wait i just realised youre not the person i was replying to lol just so you know my first sentence "about the pregnancy" is referring to Jazz Boy's theory hope u get my point
if he had feelings for the alpha twin, WHY did he mpregged the omega twin wtfffff