Kumagoro Saiki (斉木 熊五郎, さいき くまごろう lit. Saiki Kumagoro) is the husband of Saiki Kumi and father of Kurumi, the father-in-law of Saiki Kuniharu and grandfather of Saiki Kusuo and Saiki Kusuke.
Kumagoro is a grumpy old man who hates Kusuo's father and loves his daughter. He is actually a tsundere 
who truly wants to dote on his grandchildren. He is surprisingly getting along with Riki
- His name, Saiki Kumagoro, is a pun on the word Psychic (サイキック Saikikku).
- ↑ Japanese term for a character development process that describes a person who is initially cold and even hostile towards another person before gradually showing a warmer side over time.