Ito is a second-year high school student and an only child who has to move to a different city; her mother remarried and begins her new life as an older sister of 4 siblings!
The start of a family-love-comedy with four step-brothers ?

From Keijo Shoujo Scans:
Haruko Nanase wasn’t always the brightest student, but through sheer hard work she successfully entered a prestigious high school and is at the top of her class. While riding the train one day, she witnesses a fight involving a guy wearing the same uniform as her. When the fight is over, he demands that she pay him a fee for watching it but she escapes. The escape is not to last though, because the next day the guy turns out to be in the same class, and worse, his seat is next to hers.