Rein was called into a meeting with his party, which is the hero's party, and was told that he had been fired for being weak and not pulling his weight in fights and that he should leave all his gear behind as he left. After being used as the luggage guy, they decided to discard him like a piece of garbage. And just like that, he had been kicked out of a party he had been to. He was outside, remembering all the times he had been insulted by the members of the party, and realized that they had never liked him. But he did not know what to do with himself and his life until a group of small children came up to him and asked him to do the thing. I know it is not the thing you are thinking about. The thing is for him to tame a bird and make it greet them, which he did, and on having a conversation with them, he found out that the people did not like the hero and his party, which was why they were always harsh to him whenever he came to get gear for the team. The children then praised him, saying that he was a good and noble person and that they wanted to be like him (meaning adventurers). At that moment, he decided to become an adventurer and live his life on his terms and not on the whims of others. To die and live his life on his own terms. On getting to the guild, he found out that he knew nothing about being an adventurer, so he registered, had the rules and regulations read to him because he was a complete noob of an adventurer, and had to take a trial so that the guild could be sure that he wasn't incompetent. Because a lot of adventures would die due to incompetence, and that would make the guild look bad. And the government could be involved, depending on which business wants the government involved. So they don't just want to look bad.