Ayumi Murakoshi

The Oni-Baku meet Ayumi and Mariko at Yoron Shima in volume 1; while Eikichi sees it as a chance to ‘get lucky’, we get the impression that Ryuji is greatly taken with Ayumi. Despite the revelation that the two women are not students as they claim, but are actually teachers at their new school, the romance continues for a time, despite Fumiya Shindouji’s attempts to break them up (it turns out Ayumi was engaged to his brother, who died). However, when the pair decide to marry, Ayumi realizes that she would be ruining Ryuji’s life by denying him the experiences of youth, and she leaves on a train. Ryuji is understandably heartbroken by this turn of events. Well, at least until he meets Nagisa. But even then Ayumi, in her rare appearances, manages to turn his head, to Nagisa’s extreme consternation.

Wikipedia