Why was it said in AZ that the male lead and the second male lead were a couple?

In the anime AZ, the second male lead was the brother of the male lead, and there was a subtle emotional entanglement between them. Although the second male lead had a strong hostility towards the male lead at first, after a series of events, he gradually began to understand the male lead and developed a strong interest in him. In the anime, the emotional entanglement between the second male lead and the male lead was described very delicately. The tacit understanding and emotional interaction between them made the audience feel very warm and touching. Therefore, many people thought that the second male lead and the male lead were a pair of lovers and not ordinary brothers. This was also the audience's understanding of the relationship between the second male lead and the male lead.