Talk:Saiki Kumagoro/@comment-203.215.117.97-20161009011854/@comment-25234961-20161009040001

"Kumagoro is Kurumi's father. Apparently both of Saiki's parents had Saiki as their family name, even before they got married (Saiki's dad thinks it was fate, Saiki just thinks it was coincidence lol)"

This is the answer of the translator of SKNS manga. Also, not entirely connected to this but in Japan, it isn't uncommon for the husband to take the wife's surname instead of the otherway around. As for when it was mentioned... "'it's in ch92 when they go to visit the grandparents for the first time~ Saiki mentions it in a couple panels"