Basically, what would happen if Mahoraba's Kozue's alternate personalities all existed simultaneously.

Aizawa-san Multiplies (Japanese name: Aizawa-san Zoushoku)

One day, ordinary high school boy Souta Mizutani gets confessed to by Shino Aizawa, the "cool beauty" of the school. Before he can respond, though, three other girls that look like Shino appear and also confess their love! Turns out, after falling into a hole while going to school, she multiplied into additional Shinos that represent different parts of her personality: one is a go-getter that's always trying to do her best, one gets embarrassed easily, and one is rather perverted. (Of course, new personalities are always a possibility.) Souta does decide to go out with all the Shinos, and what follows is a sweet and funny romantic comedy.

A lot of the humor in this manga is of the boke-and-tsukkomi sort, and is definitely done well. The romance is also very nice, especially since the manga skips all of the "will they or won't they" stuff and go straight into the relationship. Some other characters also help make things interesting, such as Ozeki, Souta's childhood friend (albeit one with no romantic interest in him, thankfully), and Shino's mom. All in all, it's a lot of fun, and definitely worth a read if you have a premium CR membership. There are currently only 17 chapters out and the chapters themselves are short, so it'll be quick to catch up and start following the simulpub of this manga.