Differences Change the World when United (Lion-O x OC)

The ThunderCats continue their journey as they search for the Soul Stone, the last remaining Power Stone hidden on Third Earth. They need to find it or else it'll be found first by Mumm-Ra, who currently has the Tech Stone thanks to Pumyra. Their last battle against him wasn't successful, especially when Pumyra betrayed them and took the Tech Stone for Mumm-Ra. So the ThunderCats must keep on going if they want to stop him. Ever since the events of the siege in Avista, Lion-O has doubts on finding a love of his own. He thinks it will stay that way. But it's not going to last for much longer.

Lion-O had a dream of his past involving Cougalina, a hopeful and energetic cougar who's the crown princess of another kingdom. He remembered her as his and Tygra's good friend from their childhood days. When she finds the ThunderCats to help them, she and Lion-O are happy to see each other again.

Unknown to him, Cougalina is in love with him since their childhood. With the cougar princess joining, the ThunderCats will locate the Soul Stone, encounter more different animals and fight more enemies before they can defeat Mumm-Ra with their allies.

Along the way, Cougalina faces uncertainties toward her life. After the brothers told her about what happened since the Fall of Thundera, she slowly believes her hopes for peace between all animals on Third Earth and being Lion-O's mate are becoming false because she never came to the ThunderCats on time. Little does she know that a certain king is going to help her see how hope will always shine like a light through the darkest of shadows. In the process, he might start to notice she is something much more than the very first friend he made as a child. She's someone who is really special to him.