What see Bell in Ais and not in other girls.

What do you believe, does Bell find in Ais that he currently only has eyes for her, when there are other girls who already love him and can be just as attractive and strong as Ais.

For example, which other better personality than Syr, who always supported him and is very affectionate with him, or Ryuu who is beautiful and strong as much as Ais and has already confessed to her.

So, what make Ais so especial for Bell, or simply a love at first sight that they can't give up on.