Belgium is Netherlands' and Luxembourg's sister,[1] though it's said that they often push her around. She's cheerful and mature, but she doesn't stand out much due to the people around her.[1] She, herself, admitted that the stronger countries surrounding her make her look plain, but she tries her best nonetheless.[11]
Earlier notes describe her as a tsukkomi ("straight man") type. According to the character chart, she speaks in a Shiga dialect.[3] Volume 3 stated that she was cheerful and good-natured, but a bit nosy. However, when angered, she's scary.[12] The profile page cited her as "a diligent, kind, meddlesome and friendly older sister!" She also "loves gourmet and tasty snacks!"[5] Her home is famous for its waffles, and her gourmet tastes may be part of the reason that she finds foreign waffles to taste unpleasant.[11] Another thing her house was noted to be famous for was the Manneken Pis.[13]
For Halloween Belgium dressed as Little Red Riding Hood. She used it as an opportunity to briefly advertise a real-life Belgian horror game, The Path, based on the story of Little Red Riding Hood.[14] It was said that, as a child, she was even better at business than her brother,[10] so it's possible she's simply retained some of those business skills.
During the Christmas invasion of the Parallel nations, Belgium ran into one of the shadows at her house. Ignoring or not noticing the strange aura that they seem to radiate, she instead felt concern that he was naked in the middle of the winter, worried something horrible must have happened to him. Even though he was about to attack her, she showed him compassion and showed her sisterly traits in removing and giving him her scarf, startling him out of attacking her. She said that, even though his heart may have been cold because of whatever happened, he had to warm his body. She said that he could keep the scarf as a Christmas present and told him to go home, warm up, and get some rest, before taking her leave.[15]
A picture of Belgium had been requested on Christmas as the requester was a saxophone player and wanted a picture of the country who created them. Belgium complied, however she said that she had been holding a saxophone but it had been very frustrating, so she couldn't hold it for the picture.[16]