Although Umibōzu looks intimidating, he is actually extremely nice, and a devoted father and husband. This side of him is seen by Risa and Ōtani when they run into him during their school trip to Hokkaido. Umibōzu had found Risa's lost wallet, returning it to her, and offering her and Ōtani a ride back to their hotel. His trademark symbol is the sign of love.
Umibōzu is usually seen wearing baggy clothing consisting of a white zip-up hoodie and green cargo pants, accessorized with tennis shoes, a necklace, several rings/piercings, and either a white beanie or red baseball cap.
Umibōzu is very loving and devoted towards his wife. The story goes that they had met in high school where Umibōzu confessed to her, but she rejected him because she couldn't see herself dating her best friend. After graduation, she realized the mistake she made and that she deeply loved him, so she asked him out and the rest is history. They have a young son together who refers to his dad as "Bozu" even though Umibōzu would prefer his son to call him "papa."
Umibōzu's name is derived from a bald creature of the same name from Japanese folklore.