Kamen Rider SIN and SHF were both characters in the Kamen Rider series. However, they had different backgrounds and storylines.
SIC was one of the characters in the Masked Rider series. It was a fictional creature created by Ishimori Shotaro who coexisted with humans and possessed superhuman strength and abilities. The main purpose of the SIC is to protect mankind from the threat of evil forces. It played an important role in the story and fought with other masked knights.
In contrast, SHF was another character in the Kamen Rider series. It was a fictional creature created by Shoutarou Ishimori that coexisted with humans but was more powerful than them. SHF's goal was to replace humans as the dominant existence of the world. It played an important role in the story and fought with other masked knights.
There are some key differences between the SICs and SHF in terms of storylines. The SICs 'story revolved around protecting humans while the SHF's story revolved around replacing humans. In addition, the battle between the SICs and the SHF was also an important difference between them. The SIN and the other Masked Riders fought together to protect humans while the SHF fought alone to replace humans as the dominant existence of the world.