What is the relationship between Guo Yi and Tanjiro?

There should be no relationship between the fate of the country and Tanjiro:

Yueguo Yoriichi is a character in the comic book Ghost Blade and its derivative works. During the Warring States Period, he was the second son of the nation and the twin brother of Black Butterfly Mou, the first winding.

After Guoyuan I, the creator and user of the original breath and the breath of heaven, he was born to use breath and "penetrate the world", and his fencing talent and attainments were extremely high.

The second son of the late Lord in the Warring States period. There are twin brothers who inherited Guo and later became one of the first strings, the Black Death.

The creators and users of the initial breath and the breath of the sun are naturally able to use breath and "penetrate the world", and their fencing talent and cultivation are extremely high. They are called "God's love" by their brothers, which makes them less jealous than their brothers.

He was the first swordsman to wake up with stripes. He was born with stripes, and other swordsmen around him, including his brother Yan Sheng, were awakened by stripes.

Because of his special physique, he has become the only swordsman who has been striped for more than 400 years but can't live to be 25 years old, or even live to be over 80 years old.

Yuan Yi hasn't seen the couple since. But relying on a special method, he successfully broke through the curse of stripes and became the only striped swordsman in history who lived to be over 25 years old.