He might be amazed. Naruto is used to his own world and seeing a fan - made interpretation like an AMV fanfiction would be like seeing a new side of his story.
Deku might be completely shocked at first. Since Bakugou has always been so aggressive towards him, he would never expect such a confession. He might just stand there, mouth agape, not knowing what to say.
He might cry a lot. Deku is very emotional, and being cheated on would be a very painful experience for him. He could also get angry, which is rare for him, but this situation would be so unjust that he might not be able to hold it in. He'd probably start to question his self - worth too, thinking that there was something wrong with him that made his partner cheat.
Deku might be initially shocked. He's used to Bakugou's aggression, but an actual injury is different. He could be in pain and disbelief at first. Then, he might try to downplay it, especially if he doesn't want to cause trouble for Bakugou, because Deku is generally a very forgiving character.
Well, some might be really amazed. They could see a new side of Deku that they never knew before. His singing might show a different level of confidence or a hidden talent, so they would probably cheer him on.
Some characters might try to understand Deku's motives. Kirishima, who was close to Bakugou, would be angry at first but might also try to find out if there were any extenuating circumstances. However, many would be afraid of Deku, seeing him as a threat now that he has killed one of their own.
Once in Gacha Life, there was a girl named Lily. A group of mean characters would always make fun of her unique outfits. They would laugh and call her 'weirdo' whenever she entered the virtual schoolyard. One day, Lily decided she had enough. She started to focus on making real friends who liked her for who she was. She found a small group that loved her creativity in dressing up her Gacha character. Eventually, those bullies saw how happy Lily was and they stopped their mean behavior.
There was a Gacha Life love story of two characters, Rose and David. Rose was a bookworm and David was a sports enthusiast. They met at a club fair where David was trying to promote the sports club and Rose was looking for a reading club. By mistake, Rose walked into the sports club area and David kindly showed her the way to the reading club. After that, they kept running into each other. David started to borrow books from Rose and Rose would go to watch David's sports games. Their different interests brought them together and they fell in love.
A sad Gacha Life story could be about a character who loses their best friend in the game. For example, they might have planned to build a virtual world together, but then the friend quits playing. It makes the remaining character feel lonely and sad.