Zokuseiゾクセイ

First of all, if you're looking for a manga with a deep plot, leave now. This manga is primarily fan service. It follows the adventures of a male (who seems to change every few chapters) and a short, humorous, but mostly ecchi encounter with the various females he meets, whether it's in school, in the class room, or in the nurse's office. Each chapter is a mere 9-13 pages, and contains more fan service than needed!