I'm not sure specifically which 'galahad wife story' you're referring to. There could be many fictional or even some less - known historical stories related to a character named Galahad and his wife. Maybe it's a story from a particular book, game or local folklore.
Obviously, Galahad and his wife are the main characters. But there could be other significant characters as well. For instance, if it's in an Arthurian - style story, King Arthur himself might make an appearance and have some influence on Galahad's relationship with his wife. There could be knights who are friends or rivals to Galahad, and their actions could impact the story of Galahad and his wife. Additionally, if the story has a magical element, there could be a sorcerer or a fairy who either helps or hinders the couple.
The plot involves Rimuru's journey from being a rather weak (initially) slime to becoming a very powerful being. He meets many interesting characters. For example, there are the goblins he befriends early on. Rimuru helps them improve their living conditions. As the story progresses, he also has to deal with the threat of other more powerful monsters and even some human kingdoms that view his growing power with suspicion. In general, it's a story full of adventure, growth, and the forging of relationships in a magical and dangerous world.
The main character is Rimuru Tempest. He is a slime who has unique powers and a great deal of charisma. Another important character is Veldora, the storm dragon who befriends Rimuru. There is also Shizu, a human who has an impact on Rimuru's early development. And then there are characters like Benimaru, a powerful ogre who becomes one of Rimuru's loyal followers.