Tsubaki-chan no Nayamigoto

Tsubaki started going out with Yutaka who is in the same class after he confessed to her. No mails, very silent, at first she thought it was a "mistake" to go out with him but after realizing how pure/honest Yutaka is, Tsubaki gradually falls for him. So what are the worries that the two are facing..? (Source: Chibi Manga)