Besides the limitless clan, there were many other clans with a variety of good spirits. Some clans were strong, some were weak, but none of them were ever as strong as the limitless clan. During the 2 centuries the strongest clan disappeared, these clans helped keep a little bit of the world fully protected and held out for as long as they could. They were on the verge of collapsing until Kuroto was born.
As of modern times, these clans still thrive to this day. The 2 most powerful clans under the limitless clan are the cursed treasures clan and the light clan.
The cursed treasures clan being the ones to hold all of the dangerous spirit relics, items of immense power which can be absorbed to unleash the evil within the user who absorbed it and gain them a variety of different abilities depending upon the relic absorbed. The protectors are well trained good spirits which were specially trained by limitless clan members.
The light clan, having one of the most broken techniques, allowing them to use light however they want. Offensive, defensive, or any other strategy can be done by this method. Of course, this also means that their attacks are the speed of light. They may also use light to boost their speed, meaning they might be able to move at light speed, only if their boost is used right, making them the 2nd fastest clan, with the first one being the limitless clan.
There used to be 2 clans on the top, one being the limitless clan and the other being the curses clan. Curses and humans used to live together in peace, that is, until, a war broke out among them causing the events leading up to today to happen. This war was started by Sukura Goen, the leader of the cursed spirit clan. Sukura, who used to be a good spirit, started changing into evil ways, from small things like trash talk into big things like mass murder. He was a good spirit who got too strong, egotistical and overconfident.
With this, a few curses got inspired and mesmerized by his power, and so, one by one, curses starting going crazy and destroying human civilizations, causing to the war in which the limitless clan had to step in and drive the curses back to their small base, where they would live their life sealed off from the outside world. Kuroto.. after hearing all this from one of the good spirits in the cursed treasures clan, was determined to kill Sukura Goen when he got older. His exact words being "I'd win".