Yuki and Tohru are meant for eachother. In the anime show,(in episode 24 I think...)...
Shigure: Since Kagura and Kyo is on a date, why don't you two go on a date?
Tohru: Noo! I couldn't! I mean...(blushes)
Yuki:Yes, lets go on a date, why don't we go to out secret base.
It happened something like that. Also, it seems Yuki is complimenting Tohru such as "adorable" cute, and things like that. Yuki's always looking out for Tohru, even if his brother Ayame Sohma is over. Especially when Ayame acts flirty or Shigure
Shigure: After all, I am going to marry you someday.
Kyo and Yuki: Dam Shigure!
It just shows how Yuki loves Tohru. Although in the book,it shows "motherly figure", but in the anime it shows simply romance.
And Tohru...she simply blushes, but I would expect Tohru to feel pleasant and fall into his arms, thus, making im transform!