The first of 4 extra app-exclusive chapters. None of these have author comments, in case anyone wonders.
So yeah, this is how Mahoro first met Rei. You can really tell that Rei had ulterior motives in this encounter, likely because of his mother pushing for him to get married.
He certainly had a very different attitude before they got married, which explains how Mahoro fell for him, similarly to how in the spin-off he was very easygoing with Rio.
It really feels like a case of Mahoro was at the wrong place at the wrong time.
Thank you to the kind anonymous user who gave me access to these chapters, since they're not included in the volumes.