Joining Relationship (加わる関係) is the fiftieth chapter of the DanMachi manga.
At the Hephaestus Familia's Babel branch store, the shopkeeper noticed Bell, asking him if needed anything. Bell asked the shopkeeper if there were any works made by Welf Crozzo, causing both the shopkeeper and the red headed man he was arguing with to stare at him. After telling the shopkeeper that he had a fan, the red haired man took the armor, brought it over to Bell, and introduced himself as the Welf he was looking for.
Soon after the two made their way to the rest area to talk. Welf was surprised that Bell was younger than he was, even though he had already made a name for himself as the Little Rookie, but remembered the age didn't matter when it came to adventurers. He made sure to tell Bell not to refer to him by his surname before getting down to business. The smith revealed to him that he didn't want to let him go, especially as he was the only one that had ever bought any of his works. Bell thought that his naming sense might've been the problem but decided to keep quiet about it. Since Bell had sought out Welf' works himself, it meant that he approved of his work, and because of this Welf asked him if he would form a direct contract with him. Bell eventually accepted and agreed to add Welf to their party.
The next day, Bell, Lili, and Welf visited the 11th floor of the dungeon. Lili wasn't too happy about Welf joining their party, however he mentioned that no one in the Hephaestus Familia would go with him to the dungeon, with Bell adding that he couldn't turn him down after receiving the Pyonkichi Mk-III.