This is the first volume of "Sumomomo Momomo" (complete in 12 volumes, serialized in "Young Gangan" published by Square Enix from 2004 to 2009). The manga creator is Shinobu Ohtaka and this series is her first work.
Momoko Kuzuryu (the girl on the front cover) is the only child of the Kuzuryu clan. Her father, however, fears that someday his family, renowned for their martial arts skills, will weaken and die out unless Momoko marries a suitable young man and produces an heir to the family. And he has to be a strong martial artist. Koushi Inuzuka, a son of the rival clan, is chosen (without his knowing ) and Momoko is sent to the Inuzukas. The problem is, high school student Koushi, eager to be a lawyer, is not interested.
"Sumomomo Momomo" uses a time-tested pattern of Japanese comic - for some utterly incredible reasons (alien invasion, for instance), a girl starts living with a boy or vice versa. These comics are sometimes "fan servicy" and "Sumomomo Momomo" is no exception. It includes no nudities, but a few panty shots, though the comic's greatest merit is its often silly actions and exaggerated jokes based on Momoko's near super-human skills as a girl fighter.
One big disappointment is that this volume doesn't have some of the amusing supporting characters such as a tsundere ninja girl Iroha (read Volume 2). The "class rep" (still unnamed) will be back soon (Vol. 2 again) as a much funnier character, so please keep reading the series until it finally gets better in the next volume.
The first volume begins shakily with the unnecessary serious touch in the mid-section, which looks slightly out of place here, but the book remains enjoyable throughout.
By the way, though she looks very young, Momoko is a high school student, which means she is probably 16 year old or older and has reached the legally marriageable age in Japan (with consents from at least one parent, which she already has). Interestingly, it is Koushi who CANNOT marry her because he is a male and has to wait until he is 18 year old.