One possible analysis could be that their relationship in fanfic often showcases a strong bond of friendship. Bakugo's explosive personality and Kirishima's more stable and friendly nature create an interesting dynamic. Fanfic writers may explore how they support each other during battles or in their daily lives at school. For example, Kirishima might be the one to calm Bakugo down when he gets too riled up, and Bakugo could inspire Kirishima to be more confident in his abilities.
Kirishima is still alive in the manga. The story doesn't have that plot point. Usually, character deaths are significant events and are clearly shown if they occur.
Kirishima is from a manga/anime. His back story involves him having a sense of self - doubt initially. He admired those with strong and manly qualities. He worked hard to overcome his insecurities and develop his own strength and courage, eventually becoming a reliable hero - in - training.
One popular trope is the 'rival - turned - friends' concept. At first, Bakugo's aggressive nature might make him seem like a rival to Kirishima, but as they get to know each other better, they become close friends. Another is the 'protective' trope. Kirishima might be shown as being protective of Bakugo, especially when Bakugo's temper gets him into trouble. And vice versa, Bakugo could be protective of Kirishima in dangerous situations.
In the manga, Bakugo and Kirishima don't get together romantically. They have a strong friendship based on mutual respect and shared experiences in battles and training.