Lost Virgin Project

Makoto is a teenage girl... and a virgin. All her friends seem to already have had their first time and she acts like she has too. She's worried that soon, she will be the only virgin! After a series of events she meets a boy named Heiki. He's not just any boy, he's the most popular boy around! This is a story about Makoto and her friends' search for experience.

(from mangaupdates)