A Prince of a Friend Vol 4

From the Seven Seas Entertainment edition

OUTNUMBERED BY CLINGY SISTERS Just when it seems like Rui and his childhood friend Mia's hearts are about to start racing for each other, Yuzuki summons their older sister to try to break them up. As if they weren’t having enough trouble with one of his sisters getting in between them, now there are two! Though, with swimsuits and sleepovers in Rui’s future, keeping their brother to themselves might be a harder task than they bargained for!

Source: Penguin Random House API