Trinity Seven - 7-Nin no Masho Tsukai

Synopsis

From Yen Press: Arata Kasuga is living an ordinary life with his cousin Hijiri when a mysterious happening called a "Breakdown Phenomenon" makes her vanish before his very eyes. Determined to eradicate the Breakdown Phenomenon and get Hijiri back, Arata enrolls at Royal Biblia Academy. It's a tough road ahead but nothing's impossible when you've got seven beautiful girls, each a master of her own magical art, by your side. The romantic comedy and sometimes-serious wizard school story begins.

Synopsis & details from MangaUpdates