Hana-Kimi: For You in Full Blossom, Vol. 3

MEN AT WORK
Izumi, his friend Nakatsu and our crossdressing heroine Mizuki are hired to work at a beach chalet run by the family of weird school nurse Dr. Umeda! But when Kagurazaka--Izumi's high-jump rival--shows up with his two younger sisters in tow, the job gets personal! Kagurazaka's attractive sister Tamami has a crush on Izumi too, and she sees Izumi's classmate Mizuki as a way to find out about the object of her affections. And then someone realizes that Mizuki's actually a girl...