I apologize, English is not my first language. Tuban is the guardian of Seria. In her first life she was the only stern, so she suffered a lot, Seria couldn't be around other people, and always had a lot of injuries, it was too much power for her body to bear. She and Rouche fell in love at first sight, he asked her to marry him, she accepted. But Rigel messes everything up and Rouche dies protecting Seria, who collapses. She then asked Tuban to give her a normal life. She then sends Seria's soul to our world, she lives here until she is run over. Then comes her third life, which she kept like a book. That's why she thinks she read a story. In this third life, Michel replaces Roche and marries Lina, she dies at the hands of Callis. But her soul is indignant and does not accept this fate and Seria herself turns back time, and begins her fourth life, which is the current one. And no, Tuban has nothing to do with Rouche. He belongs exclusively to Seria. At this moment he uses Rouche's face because Rouche himself asked Tuban for this in Seria's first life. Tuban is a dragon, a huge and fierce dragon and Seria was very afraid of him. So Rouche asked Tuban to use his appearance to appease Seria and Tuban complies.
Lina is a creation of Rigel, this Lina is one of several that Rigel created and Lina discovers this. She dies helping in the final fight against Rigel. I don't like Lina, but she's just a victim used and manipulated by Rigel, she just wanted to be loved, she just wanted to be accepted and treated like a person.
So, Tuban is the Rouche of that time? (O_O)