Among the main characters besides Rimuru are Gobta. He is a goblin who is rather comical at times but also shows growth throughout the story. Then there is Diablo, a very powerful demon who becomes Rimuru's subordinate. His power and knowledge contribute to Rimuru's rise in the world of the novel. There are also other characters like Milim, a dragonoid with a child - like personality who has her own impact on the overall plot.
Milim Nava is an interesting character. She is a powerful Demon Lord with a child - like personality. She often gets involved in Rimuru's adventures in unexpected ways. Then there's Shion. She is a hobgoblin with great loyalty to Rimuru. Her over - the - top reactions and her growth in strength and character add a lot of fun to the story.
There's Veldora. He's a powerful dragon sealed within Rimuru's stomach at first. His presence has a great impact on Rimuru's growth and the story. Then there's Shion, a strong ogre who becomes one of Rimuru's loyal followers. She's known for her combat abilities. Also, Benimaru, a kijin, is an important character. He plays a key role in the development of Tempest.
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.
Rimuru is very strong in the manga. He starts off with some unique abilities and keeps getting stronger through different events and encounters. His strength is not just physical but also in his strategic thinking and leadership skills.