I do see the sexually/romantic tension, but only because the mangaka drew it that way in this chapter. What I don't see is why he drew it. They have been rivals, alright. That does come with a certain sexually tension between a boy and girl, but to actually let it bloom, he at least has to show a certain amount of niceness. Not calling her "you" is quiet on the weak end of the scope. He attacked her, slammed her into a wall (not in the good way), grabbed her, hurt her. And she did hurt him, too. And then they nearly never hold a real conversation in five years. Five years are long as a teen. It's not impossible she somehow ended up liking him, but than that girl has a really bad taste in men.