A runaway child who misunderstood freedom. 

Masumi Seki is one of Punpun's childhood friends and is best friends with Shimizu. He has a rough personality and usually has a cool, indifferent expression even when upset. There is a permanent scar above the tip of his nose that is covered by a band-aid for most of elementary school. His family owns Seki Lunches, which used to do business with the now-abandoned miso factory.