I see some people are telling me that this fanfiction is similar to 'Charm of soul pets', I honestly don't even remember how the story of that novel goes as I read it 3 years ago.
The idea of team rocket trial island is from fanfiction called Rise of Dark Pokemon which is on comrade mao, it has 1400+ chapters but its machine translated. You guys can check it if you want, in that MC is reborn again after getting killed when he was in team rocket on a mission. He starts with a Murkrow as he time travels back to his first day on team rocket and he also has a system, so you can check that out.
Again, this is not a remake of it, only the trial island part is taken from that fanfic. This is a completely different one from that.
Thank you.