KachiShiro said: Game is not my thing
So it would be a big help if you could summaries season 2 for me:)
There's no need for that you can directly watch the third one without any introduction to the new characters.
I had done that and ther was not a single thing o couldn't understand....
I'd recommend playing, or at least watching a playthrough for the story to unfold in the proper manner, but to summarise all the information that is learnt by the end:
Danganronpa 2 focuses on a new cast of 16 students of Hope's Peak Academy, who find themselves on a desert island under the pretense of being on summer holiday, and tasked with collecting "Hope," by the instruction of a sentient stuffed bunny named Usami. However, before long, Monokuma appears and takes over, turning Usami into his "sister" Monomi and informing the students that they are now in a killing game, just like in Danganronpa 1. Same rules, same stakes, same objective.
The protagonist is one Hajime Hinata, an amnesiac who cannot recall his talent, and is guided instead by only a vague yet strong admiration for Hope's Peak Academy. His classmates include Nagito Komaeda, the Ultimate Lucky Student, who initially takes on a companion role similar to Sayaka Maizono, before being replaced by Chiaki Nanami, the Ultimate Gamer, after which point Nagito takes on the role of Rival, as Byakuya did. Nagito is worth mentioning on his own due to how crucial he is to the plot; he is obsessed with Hope, but not in the way other DR characters are - He sees himself as a stepping stone for those with genuine talent, and so to develop Hope he attempts to bring about Despair.
There are many other classmates who are important at various stages but not worth mentioning in a summary, but you can have a look at their individual profiles if you want to learn about them. Fuyuhiko Kuzuryuu, Akane Owari, Kazuichi Soda, Sonia Nevermind and Hajime Hinata are the survivors, everyone else became victims or blackened.
Over the course of the story, it is revealed that DR2 is taking place in a computer simulation known as the Neo World, a program created by the Future Foundation, of which the survivors of DR1 are now part of, an organisation devoted to rectifying the BMTMAEIHH. The purpose of the Neo World is to act as a surrogate past for those put into it, erasing a part of their lives and allowing them to live it anew. The reason why this is being done to the students is simple - They were all (minus Chiaki, who is revealed to be an AI monitoring the system from within) members of Ultimate Despair, but the Future Foundation believed they if they could reverse this corruption, their talents could help rebuild society. Much is also revealed about Hajime:
Hajime was a reserve course student, someone who got into Hope's Peak by paying, rather than being scouted. However, he longed to have a talent of his own, and agreed to take part in an experiment to see if it was possible to artificially bring about talent. Extensive brain surgery turned him into Izuru Kamakura, the Ultimate Everything, named after the founder of Hope's Peak. He himself brought about the BMTMAEIHH, and he was also the one who caused Monokuma to appear in the Neo World - he brought an AI created based off of Junko Enoshima into it. However, the Neo World returned him to before the change, turning him back into Hajime, making him unware of all this.
Eventually, AI Junko is defeated with the help of Makoto, Kyoko and Byakuya sending themselves into the Neo World to give aid, and the 5 mentioned before escape to reality, though with the cost of being turned back into Ultimate Despair, after which the story ends.
I'm skipping a lot of important details, such as how all of this ties into Ultra Despair Girls, but I think that covers the crucial parts of info you need to know before DR3. Aside from all about the characters, but I really couldn't list the profiles of all 17 (18 if you count Izuru as a seperate person) new introductions, so that's something you'd need to research yourself.