The 100 Girlfriends Who Really, Really, Really, Really, REALLY Love You

Rentaro Aijo is a hopeless romantic – emphasis on "hopeless". Before starting high school he'd already confessed his love to 100 different girls, and was rejected every time. But a trip to a local shrine of the God of Love brings him good fortune, of a kind. Due to a clerical error in the heavens, Rentaro is indeed guaranteed to find that special someone – 100 of them, to be precise. He is destined to have triple-digit soulmates, and it's up to him to find them all, cherish them all, and keep this Love Hectogon stable, lest disaster befall him and his many, many, many, many loves. <em class=de-emphasized>(from manga)</em>

Synopsis from Anime News Network