It is basically Yuu Watase's take at a school story.
The underlying theme is friendship.
Tampopo starts school at a very exclusive place where all the emphasis is placed on status. No one is sincere and no one has friends based on actually liking someone...it is more based on people's status and what being friends with someone can do for you. The school has weird rules...no real plants are allowed on campus...it is a very sterile environment.
Tampopo is a very genuine person. She likes people for who they are.
She is also poor and only got into the school as an alternate.
Koki...the young man mentioned in the first post...is the first person she meets there and she declares in the opening day ceremonies that he will be her friend.
This earns her the wrath of everyone else in the school and they start calling her Weed and being mean.
At the risk of utterly spoiling the story, I'll just sum up the rest.
The group of five friends are all interesting characters.
One is the star, Tampopo.
One is a crazy computer genious.
One is a ganguro with a gangster father.
One is a rich girl whose only aim in life is to marry well.
One is indeed Koki.
Oh and there is also romance and angst...but not a lot of it.
It's a quick pleasant read.
The bonus stories in the last book are two romance one-shots.
One features some of Tampopo's friends from middle school and she makes a cameo appearance.