It is commonly referred to as AsaSey or Tsundere Federation(ツンデ連邦) in the Japanese fandom, due to the fact that both of them are tsunderes.
When Seychelles enters for her first day at the World Academy, she meets England who clamps a dog collar around her neck as he declares her to be his new colony. He uses her like a servant in the game much to his amusement and her horror. Seychelles talks in French when with England, because it annoys him(Example:he bids her "Goodnight" and she responds with "Oui"). Their relationship in the mainstream universe has not been mentioned, but in one scene of the manga, she seems to be angry at him.
Before he ruins their relationship by being his usual tsundere self, Seychelles seems to find both of these things to be sweet and endearing.
Gakuen Hetalia Portable
Event: England at the Park
Seychelles is checking on England in the park, wondering what he is doing. She finds out that England is playing in the the sandbox, practicing his black magic in front of the children, warning all of them not to pass the line he made in the sand.England begins to read his spells for the first time but, unfortunately, fails. The kids begin laughing at him for his failure. England thinks that the only way to make his magic work is by putting on more 'sacrifice'. Seychelles misunderstands this and thought that England will have to sacrifice one of the children. She decides to stop him for his act, but she was not aware of the line that England has warned the children about. England's magic is activated and candy begins to fall from the sky, leaving Seychelles paralyzed. Later on, when Seychelles wakes up, she finds herself being carried by England on his back. England apologizes for what he has done. Seychelles, who was shy, was afraid that her weight was too much for him and wanted to walk by her own, but England refused so and decided to carry her until they reach the dormitory, thinking that it is a gentlemen act. Seychelles was confused, later putting on a target to go for a diet.
Event: Acorn Gathering and Mysterious Ghost
England called Seychelles to gather acorns for the party. While gathering the acorns, she saw a bear with a transparent figure (who is revealed to be Canada) beside the bear. She thought that the figure was a ghost and tried to run away from him, noticing that later she fell into a deep hole.Canada runs after her and noticed that she fell. Canada asked for England's help, where later England manages to save Seychelles. England and Seychelles had both thought that Canada was America and both wanted to thank him for his help.Before they could however,Canada then disappers.
Time goes by and they realize that it is night period now. Both England and Seychelles are done with their jobs. Seychelles and England were both amazed and thrilled with the view of the city at night. Seychelles later sees a couple flirting with each other. Seychelles panicked and thought that the place was for couples. England, who also panicked, thought that everything was just a coincidence, thinking that it was not the reason why he had brought her there at the first place. England said to Seychelles that he wouldn't mind taking Seychelles back there if she likes the spot. Seychelles does like the scenery, but isn't quite sure. England then decides to bring her back to the academy.Seychelles agrees with this and they both go back to the academy.