That's not a fair assumption to make. We're introduced to her in chapter 10, and it looks like it's a pre-existing relationship so it's not quite fair to say they've developed faster.
@Kisato I didn't say that their relationship developed faster, but that they made more progress, that progress being getting married before the main characters do (if they do at all).
When Mayuko was introduced earlier on I really didn’t think they would last long much less get married. I’m glad it happened though they are both great people