ABO world view
In the early stage, the relationship between the two was very bad, they would start fighting each other when they saw each other, but in the later stage, they would be very sweet and have children.
This article is a time-travel article, so I don't know who he is below. Before differentiation, he was B. After differentiation, he was O.
Concept: There is only one orientation in this world: "the direction of the heart"