The wisest option would be C.
However, Seiji already had his own opinion of this critical question.
"I think that you should join Soul Society," Seiji stated as directly and clearly as possible.
"Why's that?" Natsuya looked directly at him.
"Because I don't think that you should be restrained by your family," Seiji told her honestly. "I once said before that you are a Yin Yang Master of the Yoruhana Family. There's nothing wrong with being loyal to the Yoruhana Family. However, loyalty doesn't mean that you should be restrained. You are an outstanding individual with talent that you deserve to be proud of. You should have more room to develop yourself."
The car fell silent for a moment.
"…Thank you." Natsuya finally spoke up after a while, breaking the silence.