I'm now nearing the end of my NG+ run and I just got back from Hawaii (in-game).
On the last night of the school trip, you get a text from a girl about spending time on the beach together after Ryuji invites you to find girls since he struck out earlier.
My first playthrough, I received a text from Makoto, who I think was my highest ranked Confidant at the time, so that made sense. However, this time around, I've maxed both Ann and Makoto's Confidant ranks, while Hifumi was only at 7, yet Hifumi was the only one who texted me.
What determines who you get a text from? It looks like only one girl will text you.