From SAKURA Chitose Fan Page:
While running to her new school in the morning of her first day, Marimo has an encounter with three guys from her school, that leave her a strange pack. Later on, in her class, the three guys appear again and kidnap her! Marimo is very scared until she realizes that they want the pack again... as it happens, they are the members of one of the school clubs... a club dedicated enterely to Kero-chans and their merchandise! (These are that typical cute Japanese green frog....) Marimo enters the club and starts to fall for the leader, but this, of course, is only the start of the fun....