Unpopular (probably) opinion on Major 2nd - I hope that Daigo and Mutsuko do not end up together.
Story-wise, both Major and Major 2nd are a testimony of their times. Major 2nd is a successor to Major, not it's clone. Daigo is not a second Goro, but a character of his own. Having Daigo marry his childhood friend would be a repetition of his father's story, which would basically void Daigo's journey and go against the theme of the new series.
More importantly - Kaoru's story was all about loving Goro and supporting him. Mutsuko's story should be about learning to value herself and realizing that she and Daigo are better off as friends than romantic partners. It would be nice, IMHO. We need stories like this.
















