Storm Lover Natsukoi!!

Original version:
Lots of bishies with one girl. Seems to have something to do with the Chinese zodiac at an elite school.

Serious version:
Igarashi Yuna is a transfer student in St. Louis High. Based on an otome game of the same name. This manga covers each of the guy's routes in each chapter.

In the series:

V.1 - Storm Lover

V.2 - Natsukoi!!