The parents!!!

There's a spin off/one shot about them called Kuroji to Harutsugu, not sure if it was translated into english yet but I've read it in spanish

You can read it here : https://qvfammaonline.blogspot.com/2019/08/kuroji-to-harutsugu-oneshot.html

There is one! Its a special one-shot called kuroji to harutsugu, at the end of vol 2, but it isn’t available on here yet lol.
(If you understand spanish you can find it on qvfamma)

AJAKSJSJSJSJ TYANK YOU SO MUCH I LOVE YOUUUU IM SO EXCITED!,,,,

I knew I should’ve taken Spanish instead of French in high school thank you so much!